iBooks To Have FairPlay DRM: Report
The majority of publishers are expected to use FairPlay for their e-books. The iBook store will sell e-books in the ePub open standard, but the ePub standard allows for proprietary DRM tools, such as FairPlay, to wrap the content.
FairPlay is used to restrict the number of devices that can access purchased content; it's usually set to 5 computers, iPods or iPhones, and the like. Of course, FairPlay has been cracked on iTunes music before; there's ever possibility that this would be cracked as well.