I got
Akimbo
was the first one i liked the look of.
Did notice that it's useful to put a .nomedia file in your audio books, to stop them showing up in normal music player apps. (just a text file, empty, with the extension changed to .nomedia)
Actually I don't use my nexus 7 for audio books, as I like to put them on an old phone, so I can slip it under my pillow, on very low volume, and drift off to a story.
Just don't feel safe doing same with the N7. But if you listen normally then a dedicated audio player is definitely worth it