Apple’s new iPad tablet device will include a proprietary e-book reader application called iBook, available for free from the App Store. iBook will use the International Digital Publishing Forum’s standard ePub format. But that does not mean that iBook e-books will be readable on other ePub-compliant devices such as the Sony Reader and Barnes & Noble Nook. Each of these devices uses its own DRM, which is not part of the ePub standard.
The “openness” of Apple’s e-book format is, thus, no more “open” than its music format was before iTunes went DRM-free: it was based on a standard codec — MPEG-4 AAC, the same as RealNetworks has used — but the files were protected by FairPlay DRM. In all likelihood, Apple will be using a variant of FairPlay to encrypt e-books from publishers that require DRM, just as it uses a variant of FairPlay for video content on iTunes.
In other words, Apple has opted to go head-to-head with Amazon, B&N, Sony, and others in the e-book reader sweepstakes — with a device that costs two to three times the prices of the others.
Apple had other choices for its iPad publishing strategy. It could have used Adobe’s Digital Editions/Content Server DRM, which is used by Sony, B&N, and most other platforms besides Amazon’s Kindle and Mobipocket — thereby providing some degree of interoperability with other readers and helping to compete with Amazon. But Apple doesn’t like getting too close to Adobe — witness the (continued) lack of Flash support on the iPad, just like on iPhones.
Apple could also have adopted an entire e-reader ecosystem that works on multiple devices in addition to its own, by acquiring one of the existing players such as Zinio or Texterity. But that would be even more out of character.
Or, Apple could have not bothered with an e-reader strategy and simply said, “We have a great SDK, and we look forward to working with publishers to develop breakthrough apps for their content.” That would have been a reasonable choice, if an underwhelming one amid all the hype.
No one doubts that Apple will be a serious contender in e-books with the iPad, especially assuming that it adapts its iBook app for iPhones and Macs (and PCs?).
So what has happened here? From this perspective, the e-book DRM mess just got messier today.
Copyright and Technology 
The iPad will use Adobe’s standard ePub format?
I think that you probably meant to say that the Apple iPad would use the open IDPF ePub, which can be enveloped in DRM, and would choose to employ its own FairPlay DRM instead of Adobe’s DRM.