The Amazon Kindle is a series of e-book readers now in its fourth generation. Amazon Kindle eReaders enable users to shop for, download, browse, and read e-books, newspapers, magazines, blogs, and other digital media via wireless networking. The hardware platform, developed by Amazon.com subsidiary Lab126, began as a single device and now comprises a range of devices - most using an E Ink electronic paper display capable of rendering 16 shades of gray to simulate reading on paper while minimizing power consumption.
Kindle hardware has evolved from the original Kindle introduced in 2007 and a Kindle DX line (with a larger screen) introduced in 2009. Announced in September 2011, the range now includes devices with keyboards (Kindle Keyboard), devices with touch sensitive screens (Kindle Touch), a tablet computer with a reader app and a color display (Kindle Fire) and a low-priced model with an on-screen keyboard (Kindle).
Amazon has also introduced Kindle software for use on various devices and platforms, including Microsoft Windows, iOS, BlackBerry, Mac OS X (10.5 or later, Intel processor only), Android, webOS, and Windows Phone. Amazon also has a "cloud" reader to allow users to read, and purchase, Kindle books from a web browser.
Content for the Kindle can be purchased online and downloaded wirelessly in some countries, using either standard Wi-Fi or Amazon's 3G "Whispernet" network. Whispernet is accessible without any monthly fee or wireless subscription, although fees can be incurred for the delivery of periodicals and other content when roaming internationally beyond the customer's home country. Through a service called "Whispersync," customers can synchronize reading progress, bookmarks and other information across Kindle hardware devices and other mobile devices. 
In the last three months of 2010, Amazon announced that in the United States, their e-book sales had surpassed sales of paperback books for the first time.
It is the only Kindle with expandable memory, via an SD card slot.
Amazon did not sell the Kindle First Generation outside the United States. Plans for a launch in the UK and other European countries were delayed by problems with signing up suitable wireless network operators.
On February 10, 2009, Amazon announced the Kindle 2. It became available for purchase on February 23, 2009. The Kindle 2 features a text-to-speech option to read the text aloud, and 2 GB of internal memory of which 1.4 GB is user-accessible. By Amazon's estimates the Kindle 2 can hold about 1500 non-illustrated books. Unlike the Kindle First Generation, Kindle 2 does not have a slot for SD memory cards. It was slimmer than the original Kindle.  
To promote the new Kindle, author Stephen King made UR, his then-new novella, available exclusively through the Kindle Store. On October 22, 2009, Amazon stopped selling the original Kindle 2 in favor of the international version it had introduced earlier in the month.
According to an early review by iFixIt, the Kindle 2 features a Freescale 532 MHz, ARM-11 90 nm processor, 32 MB main memory, 2 GB moviNAND flash memory and a 3.7 V 1,530 mAh lithium polymer battery.
On November 24, 2009, Amazon released a firmware update for the Kindle 2 that it said increased battery life by 85% and introduces native PDF support.
On July 8, 2009, Amazon reduced price of the Kindle 2 from the original $359 to $299. On October 7, 2009, Amazon further reduced the price of the Kindle 2 to $259. The Kindle 2 was criticized for its high original retail price, compared to the $185.49 manufacturing cost estimated by iSuppli.
On October 7, 2009, Amazon announced an international version of the Kindle 2 with the ability to download new titles in over 100 countries. It became available October 19, 2009. The international Kindle 2 is physically very similar to the U.S.-only model, although it uses a different mobile network standard.
The original Kindle 2 used CDMA2000, for use on the Sprint network. The international version used standard GSM and 3G GSM, enabling it to be used on AT&T's U.S. mobile network and internationally in 100 other countries.
Kindle 2 International Version is believed to have a noticeably higher contrast screen, although Amazon does not advertise this. Another review done by Gadget lab, disputes this and actually states that the font appears to be fuzzier than the first generation kindle. The review goes on to say that changes to the Kindle 2 have made it harder to read the smaller font sizes that most books use. On another website they also discuss how the font size is at times worse than the Kindle 1's. It appears that whether or not the Kindle 2 is clearer or fuzzier than the prior model depends on the font size. These issues became moot when Amazon sourced a higher contrast E Ink technology it dubbed "Pearl E-ink" and which it used in all of its e-reader devices thereafter.
On October 22, 2009, Amazon lowered the price on the international version from $279 to $259 and discontinued the U.S.-only model. On June 21, 2010, hours after Barnes & Noble lowered the price of its Nook, Amazon lowered the price of the Kindle 2 to $189.
Amazon announced the Kindle DX on May 6, 2009. This device has a larger screen than the standard Kindle and supports simple PDF files. It was also the thinnest Kindle to date and offers an accelerometer, which enables the user to seamlessly rotate pages between landscape and portrait orientations when the Kindle DX is turned on its side. It is marketed as more suitable for displaying newspaper and textbook content. The device can only connect to Whispernet in the United States. It can be distinguished from the later International version by a serial number starting with "B004".
Since January 19, 2010, the Kindle DX International has shipped in 100 countries. The Kindle DX comes with a 9.7-inch E Ink screen instead of the 6-inch basic Kindle screen. It has support for International 3G Wireless, and its serial number will start with "B005".
On July 1, 2010, Amazon released a new revision of the Kindle DX "Graphite" (3rd Generation Kindle DX). As well as dropping the price from $489 to $379, the new Kindle DX has an E Ink display with 50% better contrast ratio (due to new E Ink Pearl technology) and comes only in a "graphite" case color. It is speculated the case color change is to improve contrast ratio perception further, as some users found the prior white casing highlighted that the E Ink background is light gray and not white. Like the prior Kindle DX, it does not have a Wi-Fi connection. Its serial numbers start with "B009". The DX Graphite (DXG) is generally accepted to be of the 3rd generation, yet it is a mix of 3rd generation hardware and 2nd generation software. The CPU is of the same speed as Kindle 3 but it is of a different revision. Even though DX Graphite has a larger case, it has only a half the system memory (128MB) of the Kindle 3 (256 MB). Due to these hardware differences, DXG runs the same firmware as Kindle 2 (currently at version 2.5.8). Therefore, DXG cannot display international fonts (such as the Cyrillic font, Chinese, or any other non-Latin font), and PDF and the web browser are limited to Kindle 2 features.
Amazon announced a new generation of the Kindle on July 28, 2010. While Amazon does not officially add numbers to the end of each Kindle denoting its generation, reviewers, customers and press companies often refer to this updated Kindle as the "K3" or the "Kindle 3".  
The Kindle Keyboard is available in two versions. One of these, the Kindle Wi-Fi, was initially priced at US$139 / GB£111, and connects to the Internet exclusively via Wi-Fi networks. The other version, considered a replacement to the Kindle 2, was priced at US$189 / GB£152 and includes both 3G and Wi-Fi connectivity. The built-in free 3G connectivity uses the same wireless signals that cell phones use, allowing it to download and purchase content from any location with cell service. The Kindle Keyboard with 3G is available in two colors: classic white and graphite. Both models use the newer E ink "Pearl" display, which has a higher contrast than prior displays and a faster refresh rate. However, it remains slower than traditional LCDs.
The Kindle Keyboard uses a Freescale i. MX353 applications processor, Freescale MC13892 power management chip, Epson EINK controller and Samsung DRAM and flash. Other hardware changes include a larger 1,750 mAh lithium-ion polymer battery, AnyDATA DTP-600W 3G GSM modem and Atheros AR6102G 802.11bg Wi-Fi chip.
The third-generation Kindle is 0.5 inches shorter and 0.5 inches narrower than the Kindle 2. It supports additional fonts and international Unicode characters, and has a Voice Guide feature with spoken menu navigation. Experimental features include a browser based on the popular WebKit rendering engine, Text-to-Speech that can read aloud the text from books and other content, and an MP3 player. Internal memory is expanded to 4 GB, with approximately 3 GB available for user content. Battery life is advertised at up to two months of reading on a single charge with the wireless turned off.
Pre-orders for the new Kindle began at the same time as the announcement of the device, and Amazon began shipping the devices on August 27, 2010 in the United States and United Kingdom. With the announcement of the Kindle Keyboard, Amazon also launched an Amazon.co.uk version of the Kindle store. On August 25, 2010, Amazon announced that the Kindle 3 was the fastest-selling Kindle ever.
In late January 2011, Amazon announced that digital books were outselling their traditional print counterparts for the first time ever on its site, with an average of 115 Kindle editions being sold for every 100 paperback editions.
An ad-supported version, the "Kindle with Special Offers" was introduced on May 3, 2011, with a price reduction of $25 less at $114. On July 13, 2011, Amazon announced that due to a sponsorship agreement with AT&T, the price of the Kindle 3G with Special Offers would be lowered to $139, $50 less than the Kindle 3G. With the 2011 Kindle announcement, the price of the "Kindle Keyboard with Special Offers" was reduced to $99.
The Kindle Keyboard generally received good reviews after launch. In their Kindle Keyboard Review, Review Horizon, describes it as offering "the best reading experience in its class" while Engadget says "In the standalone category, the Kindle is probably the one to beat".
After the introduction of the low priced Kindle version, and Kindle Touch and Kindle Fire readers in September 2011 Amazon began describing the older Kindle version as the 'Kindle Keyboard' instead of the Kindle 3.
Amazon announced the fourth generation Kindle on September 28, 2011, offering models with and without ad-support, retailing for $79 and $109 respectively. Retaining the 6 inch e-ink display of the previous Kindle model as well as Amazon's experimental web-browsing capability (when within Wi-fi range), the fourth generation Kindle features a slightly smaller and lighter form factor as well as five hard keys, a cursor pad, an on-screen rather than physical keyboard, a flash storage capacity of 2GB, and an estimated one month battery life.
Amazon announced a touchscreen version of the Kindle on September 28, 2011; available with Wi-Fi ($99 ad-supported, $139 no ads) or Wi-Fi/3G connectivity ($149 ad-supported, $189 no ads). Via 3G the device is able to connect to the Kindle Store, download books and periodicals, and access Wikipedia. Experimental web browsing (outside of Wikipedia) on Kindle Touch 3G is only available over Wi-Fi.  . The device uses the same 6-inch E-ink screen of the previous Kindle model, with the addition of an infrared touch-screen control. Like its predecessor, the Kindle Touch has a capacity of 4 gigabytes and battery life of two months. The Kindle Touch began to ship on November 15, 2011 (U.S. only). Amazon announced in March 2012 that the device would be available in the UK, Germany, France, Spain and Italy on April 27, 2012
See main article: Kindle Fire. Amazon announced an Android-based tablet with a color touch screen on September 28, 2011. It costs $199 and has a 7-inch IPS display. This is the first Kindle without an E Ink display. Unlike previously released Kindles, it has no 3G option. The Kindle Fire also has an unused light sensor but lacks a microphone, camera, and an SD card reader. It has 8GB of storage and a projected battery life of up to eight hours. 
Amazon released a "Kindle for PC" application in late 2009, available as a free download for Windows 7, Vista, and XP. This application allows thousands of books to be read on a personal computer in color, with no Kindle unit required, as e-books can simply be purchased from Amazon's store. Amazon later released a version for the Macintosh, in early 2010. In June 2010, Amazon released a "Kindle for Android" version. With the Android application release, versions for the Apple iPhone, the iPad, Windows and Mac computers, and BlackBerry cellphones are also available. In January 2011, Amazon released Kindle for Windows Phone 7. In July 2011, Kindle for HP TouchPad (running under WebOS) was released in the US as beta. At this writing (November 2011) Amazon has expressed no interest in releasing a similar application for Linux.In August 2011, Amazon released an HTML5 based webapp supporting Chrome and Safari Browser called Kindle Cloud Reader.
Specific Kindle sales numbers are not released by the company; however, Jeff Bezos, founder and CEO of Amazon.com, stated in a shareholders' meeting in January 2010 that "millions of people now own Kindles." According to anonymous inside sources, over three million Kindles have been sold as of December 2009, while external estimates, as of Q4-2009, place the number at about 1.5 million. According to James McQuivey of Forrester Research, estimates are ranging around four million, as of mid-2010. On March 6, 2011, AT&T stores officially started sales of the Amazon Kindle.
In 2010, Amazon remained the undisputed leader in the e-reader category, accounting for 59% of e-readers shipped, and it gained 14 percentage points in share. According to an IDC study from March 2011, sales for all e-book readers worldwide reached 12.8 million in 2010; 48% of them were Kindle models.
In December 2011, Amazon announced sales figures for the first time: since the end of November customers bought "well over" one million Kindles per week; this includes all available Kindle models and also the Kindle Fire tablet.
Content from Amazon and some other content providers is primarily encoded in Amazon's proprietary Kindle format (AZW). It is also possible to load content in various formats from a computer by simply transferring it to the Kindle via USB (for free) or by emailing it to a registered email address provided by Amazon (for a fee via 3G, or free via Wi-Fi); the email service can convert a number of document formats to Amazon's AZW format and then transmit the result to the associated Kindle over Whispernet. In addition to published content such as books and periodicals, Kindle users can also access the Internet, free of charge, via either Wi-Fi or 3G.
International users of Kindle pay different prices for books depending on their registered country. For U.S. customers traveling abroad, Amazon originally charged a $1.99 fee to download books over 3G while overseas. That charge was quietly dropped in May 2010. Fees remain for wireless delivery of periodical subscriptions and personal documents.
In addition to the Kindle store, paid content for the Kindle can be purchased from various independent sources such as Fictionwise, Mobipocket and Baen Ebooks. Public domain titles are also obtainable for the Kindle via content providers such as Project Gutenberg and World Public Library. A survey has revealed that the Kindle store has more than twice as much paid content as its nearest competitor, Barnes and Noble.
The device is sold with electronic editions of its owner's manual; the U.S. version also includes the New Oxford American Dictionary and the UK version the Oxford Dictionary of English (not to be confused with the Oxford English Dictionary). Users are able to purchase different dictionaries from the Kindle store as specified in the included manual.  The Kindle also contains several free experimental features including a basic web browser. Users can also play music from MP3 files in the background in the order they were added to the Kindle. Operating system updates are designed to be received wirelessly and installed automatically during a period in sleep mode in which wireless is turned on.
The Kindle 2 (U.S. and International) added native Portable Document Format (PDF) capability with the Version 2.3 firmware upgrade. Earlier versions could not generally read PDF files, but Amazon provided "experimental" conversion to the native AZW format, with the caveat that not all PDFs may format correctly. Kindle 2 added the ability to read Audible Enhanced (AAX) format, but dropped the ability to read Audible versions 2 and 3.
On the Kindle 2, it was possible to view HTML files that were stored directly on the unit itself. This allowed creation of local offline content in linked web-pages that could be used even if the unit had no active connection to the internet at the time. Such pages could be accessed by directing the browser address to the local filesystem (for example, file:///mnt/us/test.html) as opposed to a live website address (for example, Wikipedia). The Kindle 3 is not able to browse local HTML in this manner, only live external websites.
The fourth generation Kindle, Kindle Touch and Kindle Touch 3G are able to display Kindle (AZW), TXT, PDF, unprotected MOBI, and PRC files natively. HTML, DOC, DOCX, JPEG, GIF, PNG, and BMP are usable through conversion. The Touch and Touch 3G versions are also able to play Audible (Audible Enhanced (AA, AAX)) and MP3 files. . Amazon has indicated that within the coming months, firmware will be released to the fourth generation kindles that allows them to support Amazon's new format, KF8.  . KF8 supports a subset of HTML5 and CSS3 features, while also acting as a container for a backwards compatible MOBI content document. 
Amazon offers an email-based service that will convert JPEG, GIF, PNG and BMP graphics to AZW. Amazon will also convert HTML pages and Microsoft Word (DOC) documents through the same email-based mechanism, which will send a Kindle-formatted file to the device via 3G for $0.15 per MB or via WiFi for free. However, the free WiFi conversion is not available to customers outside USA and UK, and this fact is not revealed to the customer until after the purchase has been made. These services can be accessed by sending emails to
The Kindle platform cannot use documents in the international EPUB ebook standard format. However there is software available (e.g., calibre) which can convert a non-DRM EPUB file into the unprotected Mobipocket format that the Kindle can read. Additionally, Amazon offers a free program called KindleGen which converts EPUB and several other formats.
A book may be downloaded from Amazon to several devices at the same time. The devices sharing the book must be registered to the same Amazon account. A sharing limit typically ranges from one to six devices, depending on an undisclosed number of licenses set by the book publisher. When a limit is reached, the user must remove the book from some device or unregister a device containing the book in order to add a book to another device.
The original Kindle and Kindle 2 did not allow the user to organize books into folders. The user could only select what type of content to display on the home screen and whether to organize by author, title, or download date. Kindle software version 2.5 (released July 2010) allowed for the organization of books into "Collections" which roughly corresponds to folders except for the fact that a collection can not include other collections, and that one book may be added to multiple collections. These collections are normally set and organized on the Kindle itself. calibre has a plugin that makes it possible to organize these collections on a computer. There remains no option to organize by series or series order, as the AZW format does not possess the needed metadata fields.
Users can bookmark, highlight and look up content. Pages can be dog-eared for reference and notes can be added to relevant content. While a book is open on the display, menu options allow users to search for synonyms and definitions from the built-in dictionary. The device also remembers the last page read for each book. Pages can be saved as a "clipping", or a text file containing the text of the currently displayed page. All clippings are appended to a single file, which can be downloaded over a USB cable. Due to the TXT format of the clippings file all formattings like bold, italics, bigger fonts for headlines etc. are stripped off the original text. But not only that, the clippings file does not keep paragraph breaks, which means the clipping is, as long it may be, completely unstructured.
On July 18, 2011, Amazon began a program that allows college students to rent Kindle textbooks from three different publishers for a fixed period of time.
On January 21, 2010, Amazon announced the forthcoming release of their Kindle Development Kit. Their aim is to allow developers to build 'active content' for the Kindle, and a beta version was announced with a February 2010 release date. A number of companies have already experimented with delivering active content through the Kindle's bundled browser, and the KDK promises 'sample code, documentation and the Kindle Simulator' together with a new revenue sharing model for developers.
The KDK is based on the Java Programming Language, specifically, the JSR 1.1.2 Personal Basis flavor of packaged Java APIs.
Kindle store offers over 200 items labeled as active content  . These items include simple applications and games, including a free set provided by Amazon Digital Services  . To the date the active content is only available in the US (or with US billing address).
Concurrently with the Kindle device, Amazon launched Kindle Direct Publishing, where authors and publishers independently publish their books directly to Kindle and Kindle Apps worldwide. In open beta testing as of late 2007, the platform has been promoted to established authors by an e-mail and by advertisements at Amazon.com. Authors can upload documents in several formats for delivery via Whispernet and charge between $0.99 and $200.00 per download.
In a December 5, 2009 interview with The New York Times, CEO Jeff Bezos revealed that Amazon.com keeps 65% of the revenue from all ebook sales for the Kindle. The remaining 35% is split between the book author and publisher. After numerous commentators observed that Apple's popular App Store offers 70% of royalties to the publisher, Amazon began a program that offers 70% royalties to Kindle publishers who agree to certain conditions.
Other criticisms involve the business model behind Amazon's implementation and distribution of e-books.  Amazon introduced a software application allowing Kindle books to be read on an iPhone or iPod Touch. Amazon soon followed with an application called "Kindle for PCs" that can be run on a Windows PC. Due to the book publisher's DRM policies, Amazon claims that there is no right of first sale with e-books. Amazon states they are licensed, not purchased; so unlike paper books, buyers do not actually own their e-books according to Amazon. This has however never been tested in the courts and the outcome of any action by Amazon is by no means certain. The law is in a state of flux in jurisdictions around the world. 
On July 17, 2009, Amazon.com withdrew certain Kindle titles, Animal Farm and Nineteen Eighty-Four by George Orwell, from sale, refunded the cost to those who had purchased them, and remotely deleted these titles from purchasers' devices after discovering that the publisher lacked rights to publish the titles in question. Notes and annotations for the books made by users on their devices were left in a separate file, but "rendered useless" without the content they were directly linked to. The move prompted outcry and comparisons to Nineteen Eighty-Four itself. In the novel, books, magazines and newspapers in public archives that contradict the ruling party are either edited long after being published or destroyed outright; the removed materials go "down the memory hole", nickname for an incinerator chute. Customers and commentators noted the resemblance to the censorship in the novel, and described Amazon's action in Orwellian terms. Some critics also argued that the deletion violated the Kindle's Terms of Service, which states in part:
Amazon spokesman Drew Herdener stated that the company is "… changing our systems so that in the future we will not remove books from customers' devices in these circumstances." On July 23, 2009, Amazon CEO Jeff Bezos posted an apology about the company's handling of the matter on Amazon's official Kindle forum. Bezos said the action was "stupid", and that the executives at Amazon "deserve the criticism received."
On July 30, 2009, Justin Gawronski, a Michigan high school senior, and Antoine Bruguier, a California engineer, filed suit against Amazon in the United States District Court for the Western District of Washington. Gawronski argued that Amazon had violated their terms of service by remotely deleting the copy of Nineteen Eighty-Four he had purchased, in the process preventing him from accessing annotations he had written. Bruguier also had his copy deleted without his consent, and found Amazon practiced "deceit" in an email exchange. The complaint, which requested class-action status, asked for both monetary and injunctive relief.  The case was settled on September 25, 2009, with Amazon agreeing to pay $150,000 divided between the two plaintiffs, on the understanding that the law firm representing them, Kamber Edelson LLC, "...will donate its portion of that fee to a charitable organization...". The settlement also saw Amazon guaranteeing wider rights to Kindle owners over their eBooks:
For copies of Works purchased pursuant to TOS granting "the non-exclusive right to keep a permanent copy" of each purchased Work and to "view, use and display [such Works] an unlimited number of times, solely on the [Devices]. . . and solely for [the purchasers'] personal, non-commercial use", Amazon will not remotely delete or modify such Works from Devices purchased and being used in the United States unless (a) the user consents to such deletion or modification; (b) the user requests a refund for the Work or otherwise fails to pay for the Work (e.g., if a credit or debit card issuer declines to remit payment); (c) a judicial or regulatory order requires such deletion or modification; or (d) deletion or modification is reasonably necessary to protect the consumer or the operation of a Device or network through which the Device communicates (e.g., to remove harmful code embedded within a copy of a Work downloaded to a Device).
On September 4, 2009, Amazon offered affected users a restoration of the deleted ebooks, an Amazon gift certificate, or a check for the amount of $30.
In December 2010, three eBooks by author Selena Kitt were removed due to violations of Amazon's publishing guidelines. For what Amazon describes as "a brief period of time," the books were unavailable for redownload by users who had already purchased them. This ability was restored after it was brought to Amazon's attention; however, no remote deletion took place.