According to Baudelaire, the devil’s best trick was to convince us that he doesn’t exist. But for Joris-Karl Huysmans, though he doubted the existence of God, belief in the devil was never a problem. For him the devil may not have been omnipresent, but he was certainly ubiquitous. Almost to his dying day, Huysmans shielded himself against the Prince of Darkness with amulets, votive statues, and talismans of all sorts. His bachelor apartment reeked with the fumes of holy tapers, left burning all night to discourage succubi and “ecclesiastical larvae” (presumably the ghosts of defrocked priests). Even garish ecclesiastical furnishings, all the vulgar paraphernalia of late-nineteenth-century French Catholicism, struck him as mischievous interventions of the Lord of the Flies. And yet, faith in the devil led him, by slow and torturous routes, to a fervent piety. The irony was not lost on him. “With his hooked paw the devil drew me to God,” he noted late in life.

There is an astonishing photograph of this fitful Satanist amid a throng of pilgrims at the Grotto of Lourdes. Taken in September 1904, it shows Huysmans wedged in with other rapt devotees before the basilica. With his neatly trimmed goatee, close-cropped skull, and impeccable frock-coat, he cuts a strangely stylish figure in the crowd. In other photographs taken at Lourdes, he has a sleek look, his delicate features giving him the unexpected aspect, amid the blurred hordes, of an elegant ferret. The sometime dandy and the lifelong bureaucrat have coalesced