The City & The City by China Miéville (034549752X). At first I had trouble suspending disbelief on the premise, but the book was so well written that the suspension happened anyway. How? The author stuck to the premise perfectly, creating a perfectly self-consistant world. I was somewhat upset that even though most of the mysteries of the book were resolved in the final act, the wierd history was never really explained.
When I was looking for downloadable audiobooks from the public library, I checked out the audio version of The Great Gatsby by F. Scott Fitzgerald (0743273567), and read by Alexander Scourby (1602834725). I'm glad I finally got around to this one; I keep telling myself that I'll read all the classics of American literature, but I never did, until I got started on the idea of listening to audiobooks while bicycling.