What was the title of C.S. Lewis’s 1942 book based on demonic letters to a junior tempter?

The Screwtape Letters is C.S. Lewis’s 1942 book presented as correspondence from a senior demon to a junior tempter. The senior demon, Screwtape, advises his inexperienced nephew Wormwood about tempting a human patient.

Lewis uses the fictional letters to discuss temptation, pride, distraction, resentment, fear, and self-deception. Because the advice is written from the demons’ viewpoint, the book relies on irony: readers are meant to infer the moral and spiritual lessons by recognizing the distortions in Screwtape’s guidance.

The work first appeared in serial form in the Anglican newspaper The Guardian before being collected as a book. It became one of Lewis’s most widely read works of Christian apologetic fiction. The demonic narrator is not Lewis’s spokesman; the character’s manipulative arguments are deliberately presented as the opposite perspective.