Just wanted to share my little audiobook player project.
I am using a Pirate Audio Hat on a Pi Zero as a simple audiobook player. The app lets you choose an audiobook, navigate in it, set a sleep timer and toggle wifi on and off. I run it in Openbox after booting. Playback is handled by python-vlc.
Our audiobooks are all in m4a format and quite long, so it is sufficient to load only one file at a time.
More info and code at Github Audiobookplayer