The Jam is a MSC-only player. MTP mode I believe is required for audio books you ‘borrow’ from the library using Overdrive to download them, so I don’t think the Jam is the right player for you if that’s what your main purpose for it is. Try and find a Clip+ or Zip instead.
From the Clip Jam Support Information page:
NOTE: Clip Sport/Jam supports audiobooks obtained from Audible and DRM free Audiobooks only.
