The name Richard Castle is also used as a pseudonym under which a set of real books about the characters Derrick Storm and Nikki Heat, based on the books mentioned in the television series, are written. These books have achieved success, becoming "New York Times" bestsellers. Actor Nathan Fillion appears as the face of Richard Castle on the books and on the official website, and participates in book signings. The Castle book series was actually written/ ghost-written by screenwriter Tom Straw.