Book / Audiobook Recommendations?

Any suggestions on what audiobooks I should look for next? Or if you don't know audiobooks as much as any ol' books, recommend one there too. I prefer sci/fan, especially ones that play with the border between the Sci-Fi and Fantasy. Hard science without good characters and plot (like Gregory Benford) drives me insane, but speculative fiction where some new scientific breakthrough drives the characters and story (like Larry Niven) is awesome. I prefer adult to young adult, but I don't mind young adult. I don't mind serieses just so long as there are fewer sequals than letters in the author's name.