How to sync audio books to iPhone?

I have some audio books on my iPhone from a while back. I added a new audio book to Books on my desktop. I expected it to show up on my iPhone, since I sync books over icloud. The new book didn't show up. In the end, I connected my phone with a usb cable to my desktop, and discovered that the only thing I apparently have ever synced in the recent past using this approach were (wait for it) Audiobooks!

Apparently it has been a while. Technically my audio book was a spoken word mp3 which I wanted to listen to like an audio book since I wanted the +/- 10 seconds feature that is not there in the music player app.

Is syncing over the cable really the only way for audio books to get on my phone?