Overlooked in much of the hype about the iPad announcement earlier in the week was a comment by Steve Jobs in the Keynote presentation where he mentioned that the iBooks app for iPad would take advantage of the popular EPUB format for electronic books.
EPUB is the same format used by the popular Stanza [free, iTunes link] app for iPhone and iPod touch. It’s a free and open standard format created by the International Digital Publishing Forum (IDPF), and it’s designed for reflowable content that can be optimized to whatever device is being used to read a book file.
ebook readers that currently use the format include the Barnes & Noble Nook, the Sony Reader, iRex Digital Reader, and the iRiver Story.
Read more at All about EPUB, the ebook standard for Apple’s iBookstore.
Does this mean that Apple might be pushing for a robust EPUB standard.
(I do like the Shelfari-look on that screen!)
judyoconnell.com 
Please don’t forget that EPub is not a panacea. As long as an e-book is protected with DRM, the format is moot because the book will likely be readable on only a single, specific device anyway. Kindle’s a little better, because it stores purchases in ‘the cloud’ — so if you de-register one Kindle and re-register another, your library alters to fit. But Amazon’s format only works with Kindle, were DRM’ed books are concerned. I think the Nook may be the same way; it has just now occurred to me to wonder how the Sony Reader deals with DRM.
Just like if you had to re-buy all of your CD’s every time you bought a new CD player.