Camp Haunted Hills Series by Bruce Coville

There are weird goings-on at Camp Haunted Hills! Are these all special effects created by the filmmaker who runs the place or is the camp haunted for real?

Stuart returns to movie camp for the summer, and finds that his fellow campers are turning into monsters--without the help of makeup or special effects.

Stuart looks forward to another adventurous summer at Camp Haunted Hills, but he gets more than he bargained for when he and his friends inadvertently travel back to the time of the dinosaurs.