I used to think that Dan Brown was merely bad. Now, after reading the latest version of the apocalyptic thriller he rewrites every few years, I suspect he might be mad as well. "Inferno" begins with the hero suffering from "head trauma," and Brown's head — a boggy hideout for the craziest superstitions of the so-called Dark Ages — seems to be similarly traumatized.

INFERNO, by Dan Brown. Bantam, 2013, 480 pp., $29.95 (hardcover)

Brown views creation as a cryptogram and babbles about murderous albino priests, self-gelded ogres and a female devil who dresses in black leather and bestraddles a motorbike; he is fiendishly elated by the prospect of the world's imminent demise. Hogwarts Academy, compared with Brown's brain, is a clean, well-lighted, supremely lucid place.