Do you like audio books? Then lets get cozy!
Cozy is a audio book player. Here are some of the features:
Somehow didn't detect a single folder as a whole book. Also don't have any normal management features.
Works great except for the fact you can't remove anything from the library unless you delve into your file system, find the right folder and nuke all of it then rescan the library. Not sure how they could mess up removing books once you have listened to them but the Flatpack version seems to have no way to do it.