Add a menu item to the left hand library navigation called 'AudioBook'. Currently I have to mix these up with my music, making random play of my whole library a bit of a pain, and not allowing me to effectively organize my audio book collection (I have had to move them to a separate folder and use an other application to play them, would like to keep them within rhythmbox)

Alternatively, but probably more work, would be to allow user to add their own custom libraries to this list.

Cheers,
Bert