Cujo by Stephen King
Outside a peaceful town in central Maine, a monster is waiting. Cujo is a two-hundred-pound Saint Bernard, the best friend Brett Camber has every had. One day Cujo chases a rabbit into a bolt-hole - a cave inhabited by sick bats. What happens to Cujo, how he becomes a horrifying vortex inexorably drawing in all the people around him makes for one of the most heart-stopping novels Stephen King has written.