Which C.S. Lewis book features the demon named Screwtape?

The C.S. Lewis book featuring the demon Screwtape is The Screwtape Letters.

Published in book form in 1942, The Screwtape Letters presents a series of fictional letters from Screwtape, an experienced demon, to his inexperienced nephew Wormwood. Screwtape advises Wormwood on how to tempt a human being and interfere with that person’s spiritual development.

Lewis uses an unusual reversed viewpoint: the narrator is a demon, while the intended human target is called “the Patient.” This structure lets Lewis satirize pride, distraction, self-deception, resentment, and other moral weaknesses. The letters are fictional, but their subjects reflect Lewis’s Christian understanding of character and temptation.

The book is sometimes confused with The Great Divorce, another Lewis work involving an imaginative journey and the afterlife. The Screwtape Letters is much more specifically organized around correspondence between two devils. Its epistolary format remains one of Lewis’s most distinctive literary devices.