The Sexorcist — Wayne Mansfield

As an atheist, Calvin Deeds has no truck with either God or the devil. So when he's possessed by an evil spirit who calls itself Satan, he doesn't believe it. But the manifestations are horribly persuasive, the house shakes, and he is flung around the room. He flees his house, but the spirit follows him to his best friend Graeme's house, where it takes over completely.

Now Graeme has to deal with the horny and provocative spirit using Calvin's body. As a last resort, he contacts Father Gregg, the local parish priest. Initially reluctant, Father Gregg soon has to face down the evil spirit, and his dedication to his own vows of chastity.