The Kindle is not compatible with the popular ePub e-book format.
All digital reading material purchased or downloaded from the online Kindle bookstore is in Amazon.com's proprietary AWZ e-book format. The Kindle is able to read a variety of other e-book formats besides AWZ files, however, which can be uploaded from your e-book library on a computer, downloaded from an alternate online e-book repository, or viewed through the Kindle's Web browser.
MOBI and PRC
The MOBI e-book format was devised by the Mobipocket company, which was subsequently bought by Amazon.com. Amazon.com based its proprietary AWZ e-book format on the MOBI standards, which in turn was based on the Palm Pilot's PRC format. Therefore, both MOBI- and PRC-formatted e-book files are fully compatible with the Kindle, and offer active index pages, illustration and full text formatting. Any MOBI or PRC e-books you want to view on the Kindle must not have any encryption or copyright protection, however.
Adobe's portable document format was devised in 1993 as a universal digital document platform that contains layout formatting as well as text and images. The purpose of the PDF format was to provide digital documents that would look exactly the same on any software or hardware platform. The Kindle is compatible with PDF files, though due to the device's display restrictions it isn't always able to correctly format complex PDF e-books. Because of this, PDF compatibility with the Kindle is considered experimental.
Online E-book Resources
E-books in a variety of different formats are available from online resources besides Amazon.com, and can be used to acquire new content for your Kindle. Services such as Fictionwise, ManyBooks and Project Gutenberg provide thousands of copyright-free e-books, which can be downloaded to your computer in Kindle-compatible MOBI or plain text formats, and then transferred to the device via USB. Some of these services also allow you to email e-books directly to the Kindle from their websites.
Web Browser
Some online e-book repositories, such as Google Books, allow you to read copyright-free and licensed e-books directly from within your computer's Web browser, as well as downloading them for offline viewing. The Kindle also has a built-in Web browser, which is accessed through the "Experimental" section of its "Settings" menu. By logging into your Google account through the Kindle's Web browser, you can read these online e-books. An active Internet connection is required to load new pages, however.
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