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