Responding to my request for how to make an ePub book from an InDesign file, Toli Galanis writes:

My copy of Elizabeth Castro's "EPUB Straight to the Point: Creating ebooks for the Apple iPad and other ereaders" has a chapter called: "Using InDesign to Create EPUB."

You can buy the book here (I make no money off this)

Seth Godin wrote about book ideas for the iPad in the past, here and here, and I know that this is ripe for experimentation and innovation.

I just bought Castro's book and it looks very good. More after we've had a chance to use it.