Leven's first novel, Creator, was published in 1980 and released as a film of the same title in 1985. Leven was a practicing neuropsychiatrist, a theme incorporated in his second novel, Satan, His Psychotherapy and Cure by the Unfortunate Dr. Kassler, J.S.P.S., which was published in 1982 and filmed as Crazy as Hell in 2002. His most recent novel, The Savior and The Singing Machine, was published in January 2019.