James Paul Czajkowski, who writes under the pen name James Rollins, is an American veterinarian and author of action-adventure, thriller, mystery, and techno-thriller novels. He left his veterinary practice in Sacramento, California to pursue writing full-time. Rollins draws heavily on his personal experiences and expertise in his fiction. As an amateur spelunker and certified scuba diver, he frequently incorporates underground and underwater settings into his novels, lending them authenticity and technical detail. In addition to his work as James Rollins, he has published fantasy novels under the pen name James Clemens, including the Wit'ch series (Wit'ch Fire, Wit'ch Storm, Wit'ch War, Wit'ch Gate, and Wit'ch Star) as well as Shadowfall and Hinterland.