Did you read the iTunes small print?

iTunes 10.3 also adds Books to the iTunes Store, when you discover how to buy your favorite books on your computer and automatically download them to iBooks on your iPhone, iPad, or iPod touch, we won't tell you how because life is an adventure and we would not want to spoil the frustrating experience for you. This version also allows you to use Automatic Downloads with apps and books or download previously purchased apps and books from your computer or iOS device.