John Sandford's books are good on audio, Virgil Flowers is growing on me.
I liked The Devil Wears Prada on Audio and after I got used to the sucky narrator I liked all the Hunger Games books on Audio
The early Nelson DeMille are good on audio but his latest, The Panther (I think) sucked. Audible gave me my credit back because I gave it a crappy review
murder mysteries are the best to me on audio. I like JD Robb but they are a formula and futuristic so not for everyone
And the Sookie Stackhouse books are great on audio if you like vampires!