Beat the Reaper by Josh Bazell
It's been a long time since I read a debut writer with the pace, humor and hard-boiled, powder-burned worldview of an Elmore Leonard. Who knows where he got 'em, but Josh Bazell has 'em. His hero is Peter Brown, a former Mob hit man who has witness-protected himself into a medical residency at a New York hospital. Surprise, surprise, his old life comes around looking for him. The book takes us careering through a crime-thriller plot, but the story is salted with a lot of really fascinating insider medical know-how and peppered with all kinds of ballistics lore and martial artistry. This is a hit man who knows in anatomical detail exactly how he's damaging you ("the two bones of the forearm, the ulna and the radius, move independently of each other..."). I defy you to put it down.