May I ask how that worked out for you? I, too, am searching for Part 1 of a 2 part audiobook. I found Part 2 on my MacBook Pro. Both seem to be syncing with the cloud. But, I have these 2 parts split between the two.
I don't want to sync to iTunes on the Mac because the iPhone is most up to date.
Have you found a way to get a book you've purchased to your iPhone?
I know about the iBooks app. Audiobooks go into iTunes on the iPhone, too.
Searching for an answer.