EPub, an open and widely-used format for eBooks, is a great ideal, but, as Gizmodo points out in a lengthy post running down the various eBook and DRM formats, but various companies different kinds of DRM basically kills the promise of eBooks compatible across devices.
Most companies, says Gizmodo, use Adobe’s DRM. But Amazon’s got its own format, and Apple will be using its own FairPlay DRM. So, as you probably already know, you won’t be swapping eBooks between iPad and Kindle or Nook or anything.
Here’s the main point from Gizmodo: “You may be thinking that it’s just a matter of time before ebook stores all go DRM free. That would be wishful thinking at best. While ebooks might seem a lot like digital music circa 2005, you can’t rip a book, so the only way to get a bestseller on your reader is to buy it legally, or to steal it. It’s pretty much that simple. There will be free books, there will be unencrypted books, and the torrents will rage with bestsellers (as they already do). Still, DRM’s gonna be a hard fact of life with every major bookstore, since they’re going to at least try to keep you from stealing it. You don’t see Hollywood giving up DRM, do you?”