EPUB is a free, standardized format that almost every hardware eReader or desktop software understands. Amazon’s Kindle, however, cannot read EPUB texts without using some intermediary software that converts these books into a format the Kindle can understand. While there are a few competing formats, EPUB has turned into the de facto standard for eBooks. Some vendors, like Sony, wrap a digital rights management (DRM) solution around these books, but others just publish completely open, non-DRMed versions of their books. The EPUB files from Google Books will not be locked down by a DRM solution.
Here are some applications that can allow you to open and read an EPUB ebook.
Stanza – read EPUB ebooks on pc, mac, ipod touch and iphone.
JediSaber has a nice page reviewing all of the ebub readers listed above, but if you’re in a hurry and want to select the best to use on your operating system here’s the summary:
For Windows: Adobe Digital Editions for it’s management functions and excellent ePub format support.
OS X and/or iPhone/iPod Touch: Stanza is the winner, hands down.