Following the launch of its new education suite, Apple just launched a new version of iTunes for syncing your iBooks textbooks to your iPad. It's available for download now on Apple's site. We're not seeing it in Software Update just yet, but it should be good for download there soon.
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 Mac or from the iBookstore included with iBooks 2 on your iPad.