Alright, I just fired up iBooks Author, which is a free download from the Mac App Store. It installed quickly, and after selecting a template I was editing my first-textbook in moments. The single-window interface is just like any other modern iWorks app, and Apple isn't offering it for free for lack of features. Like Josh mentioned in the liveblog, the app is a mix of Keynote and Pages, with drag and drop layout tools and a sidebar of "slides" representing the table of contents.
Of course, the app isn't exactly designed for your mom to publish a interactive textbook of her vacation: while some aspects are a breeze, there's no WYSIWYG to build 3D objects from scratch or code HTML5 elements, you'll have to do that externally. Also, the app didn't support many of the videos in various QuickTime-supported formats on my computer (though, oddly, it embedded a music video from the iTunes Music Store), and animated GIFs seem unsupported as well. Standby for the official The Verge textbook in highschools everywhere this coming fall.
Also worth noting: nothing in this tool makes you automatically an expert on any educational topic. Luckily, this tool seems just as fitting for publishing a regular book, with fancy typography or interactivity as needed. We just hope Apple will have a close eye on its textbooks category, before somebody leads our country's young minds astray.