Moving beyond the main text, authors can also arrange glossaries by highlighting and clicking words, and clicking again to add a definition. In a surprise move, Apple also said authors can publish straight to the store, though we're waiting for clarification that textbook writers and other scribes are actually exempt from Cupertino's notorious approval process. In any case, the app is available now in the App Store (for OS X Lion only, sadly) so you can cracking on that definitive Kurt Vonnegut glossary you never knew you had in you.
Update: We've got our hands-on up!
Update 2: Apple has confirmed some key approval and revenue-sharing details. First, authors will be subject to the same App Store approval process as developers. Writers can offer their books for free, or for as much as $14.99 -- the same price cap for textbooks sold in the store. And, like developers, authors must agree to a 70/30 revenue split, with writers pocketing 70 percent after Apple takes its share.