James Paul Czajkowski, better known by his pen name of James Rollins, is an American veterinarian and writer of action-adventure/thriller, mystery, and techno-thriller novels who gave up his veterinary practice in Sacramento, California to be a full-time author. Rollins' experiences and expertise as an amateur spelunker and a certified scuba diver have provided content for some of his novels, which are often set in underground or underwater locations. Under the pen name James Clemens, he has also published fantasy novels, such as Wit'ch Fire, Wit'ch Storm, Wit'ch War, Wit'ch Gate, Wit'ch Star, Shadowfall (2005), and Hinterland (2006).