Like The Exorcist, Legion is structured as a detective story—in this case, as Douglas Winter points out, a police procedural.

We follow Kinderman searching out clues, interviewing witnesses, receiving lab reports, pursuing and eliminating suspects. In fact, even the theological/philosophical theme is presented as a process of putting clues together, and speeches by Kinderman that begin in the metaphysical may instantaneously switch to his speculations on the multiple murders under investigation. Kinderman refers to himself half-jokingly as "the Jewish Mister Moto ... on the verge now of cracking this problem of evil."

In The Exorcist, the focus on the murder mystery allows Blatty time to credibly build up clues, slowly introducing the reader to the supernatural; in Legion, Blatty presents the spiritual musings and murder investigation in counterpoint, perhaps to maintain interest among readers who care less about one aspect but will keep reading for the...