What is the book 'Master of Murder' by Christopher Pike about?

Master of Murder No one knew he was famous. Marvin was an eighteen-year-old senior in high school. He was also America's bestselling author of teenage fiction. Millions of kids read his books. In fact his latest series-THE MYSTERY AT SILVER SPRING-was the craze at his high school. But Marvin wrote under a pen name,Mack Slate, and no one knew who he was. He was rich and famous, but he couldn't even get a date for Friday night. Yet Marvin wanted to remain unknown. He was worried that his incredible career was about to hit a brick wall. The final installment of his famous series was overdue. His millions of fans were dying to know what was going to happen in his series, but so was Marvin. He had no idea how the story was supposed to end. Then one night he opens a fan letter. It has come from his publisher-in the usual way. But this letter says, "I know who you are," and the postmark is from his local town. At first Marvin is unconcerned about the letter, but then another one arrives, saying more... Soon Marvin is caught up in a web of mystery more complex and frightening than his own books. But too late he realizes that the stories he has been spinnning are true.