Which C.S. Lewis novel features the demon Screwtape writing letters to Wormwood?

The C.S. Lewis novel featuring the demon Screwtape writing letters to Wormwood is The Screwtape Letters. Lewis published the book in 1942, presenting it as correspondence from an experienced tempter to a junior demon.

The letters reverse the usual viewpoint of religious instruction: readers observe human behavior through the imagined advice of demons. Screwtape discusses temptation, distraction, pride, and relationships while trying to guide Wormwood in influencing a human subject.

Although the work is fictional, Lewis intended its satire to expose habits that can undermine moral and spiritual life. It is sometimes described as a novel, an allegorical work, or a series of epistolary essays. The book’s letter format is its defining structural feature, and it remains one of Lewis’s most widely read works outside the Narnia series.