Although I prefer horror, weird tales, and most science fiction I also enjoy good sarcastic comedy mystery type of books. One of the masters of this type of writing is Carl Hiassen but I have just found another author in the same vein. Well written, plenty of great comedy, good action, nice plot, good writing in Harlan Coben. I am almost finished with Deal Breaker and would highly recommend it to anyone. The Hero, Myron, somtime sports agent, sometime black bag FBI operations and his friend Wynn remind me of John D McDonald's work. Wynn and Myron kick and punch there way through the porn world all the while trying to get the fresh new quarterback signed to his first pro contract. If you have read any of Mr. Coben's books give it a try - they are a great break from horror and the like.
To keep on the Stephen King vein, I would highly recommend Bev Vincent's book "The Road To The Dark Tower" as a companion read while you are reading the Dark Tower series. If you have not read this series of 7 books I highly recommend them. They firmly establish the King multiverse and connect many of his others works. It becomes great fun to ponder the connection of King's work into the dark tower world.