Very good books - both Shutter Island and Mystic River.
When I finished Shutter Island, I actually turned back to the beginning and re-read it, just to see all the hints I missed to how it ended. (Not going to say more than that!)
I first discovered him on a recommendation from the local bookstore to read his detective series - I think the first book was A Drink Before the War. I read them all, one after the other. I don't remember much about them today, I'm afraid - too many books in between.