Which C.S. Lewis novel features the demon apprentice Wormwood receiving letters from Screwtape?

The Screwtape Letters features the demon apprentice Wormwood receiving advice from Screwtape.

Published in 1942, The Screwtape Letters is an epistolary Christian apologetic work presented as correspondence from a senior demon to a junior tempter. Screwtape advises Wormwood on how to influence a human subject. The unusual viewpoint lets Lewis satirize temptation, self-deception, pride, distraction, and bureaucratic thinking.

The book began as a series of letters rather than as a conventional narrative. Lewis later said the project was difficult because he had to maintain the infernal perspective. Its correspondence format makes the narrator’s advice intentionally unreliable: the demons describe their own aims, not a neutral account of morality.

The work is often grouped with Lewis’s explicitly apologetic books, but it differs in form from Mere Christianity and The Problem of Pain. It also should not be confused with The Screwtape Proposes a Toast, a later address derived from the same fictional world and published separately.