The Exorcist is a 1971 novel by American writer William Peter Blatty. The book details the demonic possession of twelve-year-old Regan MacNeil, the daughter of a famous actress, and the Jesuit psychiatrist priest who attempts to exorcise the demon. Published by Harper & Row, the novel was the basis of a highly successful film adaption released two years later, whose screenplay was also written by Blatty.