In 1976, Keene co-authored The Psychic Mafia, "as told to" Allen Spraggett, a well-known Canadian writer on paranormal topics. The writer William V. Rauscher, himself a believer in psychic powers, contributed a foreword and a bibliography and wrote that he conducted 75 hours of interviews with Keene, during which Keene admitted that all of his psychic activities were done by fraudulent means. Keene revealed how he got rich by tricking thousands of people in séances. James Randi, a professional magician, interviewed Keene in 1977, and discovered that Keene was quite unsophisticated in fooling people with magic, but Keene explained that his spiritualist clients were easy to fool. Keene described how the victims fell for the most transparent ruses. Keene coined the term true-believer syndrome in the book.

In The Psychic Mafia, Keene explicitly professed a belief in God, life after death, psychic phenomena and ESP, even after making his case against true believers and renouncing his trade as a phony medium.

Keene not only confessed that he himself was a fraudulent medium, but also that many of his colleagues were as well. He wrote that it was common practice for mediums to share information on clients, to help one another fool the clients into believing that the knowledge about them came from the spirit world. The book caused a storm among his former associates in spiritualist circles. There were telephone calls threatening his life. One night, while walking across his front lawn in Tampa, an unseen shooter fired at him and missed, and he later dug the rifle bullet out of the wall of his house.

Keene changed his name, moved to another city, and entered the warehouse and storage business. In 1979, as he was leaving his office, a car drove up and an assailant fired several shots, hitting Keene and severing his femoral artery, resulting in an extended hospital stay.