Audio Books

Over the course of the next 10 days or so, I'll be spending a lot of time in the car...we're talking 20+ hours of driving, by myself, across parts of the Midwest.  I'm not normally much of an audio book person, but when it comes to long car trips by myself, that's a different story.  So I'm looking for suggestions of good books to look for on CD!  I need something with enough action to keep me interested, but I've done all the basic genres before, from mystery to YA to romance and general fiction.  So if you have any suggestions, please let me know!