Which 1942 book by C.S. Lewis presents letters from a senior demon to a junior demon?

The Screwtape Letters is C.S. Lewis’s 1942 book presented as correspondence from the senior demon Screwtape to his inexperienced nephew Wormwood. The letters discuss methods of temptation and spiritual distraction.

Lewis uses the reversed viewpoint to make readers examine ordinary habits, motives, and moral choices. Screwtape’s advice is meant to help Wormwood undermine a human being, while the book’s satire exposes the self-deception behind that advice.

The work began as letters published in the Anglican newspaper The Guardian before appearing as a book. It is often grouped with Lewis’s Christian apologetic writing, but its fictional epistolary form distinguishes it from works such as Mere Christianity, which developed from broadcast talks.