Apple CEO Tim Cook said 400 million books have been downloaded through its iBookStore.
The iBook program also got several new features, including continuous scrolling, which eliminates pages and the need to swipe to advance.
iBook also integrates with iCloud, allowing readers to stop on one device and pick up on another device. Readers can also share a passage via e-mail or Twitter.Cook also talked up the iPad's use in the education world. Apple will make available iBooks Author, which allows publishers to do things like create a portrait-only template for books, add embedded fonts, and insert rendered mathematical expressions. Also included are multi-touch widgets for further interactive capabilities.