That's a fair point. I'm in higher education and our school doesn't buy books. I've created video lectures using Camtasia using a Wacom tablet and pen. The notes are in PDF format and I've created my own exercises. Students for one of my classes don't need to buy a book because I've got everything done for that course.

I'd like to use something like iBook Author but only if I can export it in a device independent way.