The Screwtape Letters should not work as literature—the whole thing looks bad on paper, which is rather a high hurdle for a book to overcome. The epistolary form already had been exhausted by the time C. S. Lewis turned his learned hand to it, the last vitality having been drained out of it a half-century earlier by Bram Stoker’s Dracula. As for Screwtape himself, he’s the sort of character that Oscar Wilde would have abandoned as too broad and too obvious, and even Wilde by the end of his uneven career had wearied of creating such witty cynics as the titular demon. As drama, the work has very little to offer: Screwtape reads and writes letters from and to his nephew Wormwood, an inexperienced demon just out of the tempters’ academy and set to his first task: corrupting the soul of a young Englishman. Screwtape offers advice and criticism; nobody is there and nothing happens. In short, we’re watching a bureaucrat handle his mail: not exactly the Trojan War. Worse, Lewis’s purposes are nakedly propagandistic, his little upside-down homilies oozing Anglo-Protestant contentment. You can practically smell the Easter lamb roasting.

Terrible on paper. Genius in fact.

A happy combination of factors saves Screwtapefrom being the insipid mess it might otherwise have been: One is that Lewis could write—really write, with nerve and economy—and the second is that he was not sentimental to the point of debilitation. The technical challenges of the epistolary form—not least