I import audiobooks checked out from my local library, then import them into itunes. Sometimes adjustments have to be made so the discs will link together. Once linked, I could drop in the audiobook artwork and, using the Options tab, switch the format from Music to Audiobook. Immediately, the whole thing would move from Music to Audiobooks, where it could be synced with the iPhone and iPad.
Now, there is no longer an Audiobooks tab in iTunes, only a Books tab. Worst of all, when I attempt to switch from Music to Books prior to an iPhone or iPad sync, chaos happens. Instead of the new Audiobook listing the chapters in order, e.g. Disc 1 Chapter 1a, Disc 1 Chapter 1b, Disc 1 Chapter 1c, it is ordered as Disc 1 Chapter 1a, Disc 2 Chapter 1a, Disc 3 Chapter 1a. I have tried various fixes, to no avail. When I mentioned to a young lady in an Apple store, she (and I am not kidding) said she thought many people might not mind such a thing. I told her it was nearly the dumbest thing I have ever heard in my life!
Notably, the books play just fine if you play them as Music. You can sync as Music and it also runs fine on the iPhone and iPad. Also, everything synced previously still works as before. But it is annoying and I think a sign that Apple's near supremacy in this area may have peaked - especially if they don't get this fixed very fast. If you cant trust their cross device synchronicity, their brand is weakened