Doubtless, the extreme popularity of The Exorcist, both book and movie, is due to its connection to many social issues of its time, but one should not discount other virtues of the book. While occasionally overwritten, it does excel at conveying mood; and the careful development of the events in the book made it easy for people who did not usually read supernatural fiction to imaginatively enter into it as "real." The movie broke special-effects ground and provided an emotional "rollercoaster ride," as Blatty has said. Still, these qualities alone would not have made The Exorcist the cultural phenomenon it was.

It is easy to define The Exorcist as a "horror novel," because of the genre of best sellers by Stephen King and many others that followed it. Critics have sometimes forgotten that contemporary reviewers as often categorized it as a novel about religion. Religious best...