iTunes 10.5.3 allows you to sync interactive iBooks textbooks to your iPad. These Multi-Touch textbooks are available for purchase from the iTunes Store on your PC or from the iBookstore included with iBooks 2 on your iPad.
Theres a lot of interest with this announcement of a new authoring tool for books that support this application. The general consensus is that this is yet another attempt by Apple to steal the lead on this particular area of education. Should be interest to see what is actually possible and how restrictive the authoring is.