Yeah that's what I figured, so for any book I'm attempting to create I've been .pdf'ing it first before sending it. Why? I've noticed that sometimes the .pdf file DOES NOT look like the preview. This is mostly when you use non-4:3 images for creating the book, when multiple images are on the same page. Kinda screws things up.
BTW, iBook is SOOOOOO unstable. And you can't manually save but you can force a save by exiting the program. I've taken to doing that periodically, because a few it's quit in the middle of an edit, losing my last 15 minutes of work.