Which C.S. Lewis book introduces the demon Screwtape as a senior tempter?

The Screwtape Letters introduces the demon Screwtape as a senior tempter. Published in book form in 1942, the work consists of fictional letters from Screwtape to his inexperienced nephew Wormwood, who is assigned to tempt a human being.

Lewis uses the letters to reverse the usual viewpoint of religious instruction. Instead of presenting advice from an angel or saint, he lets a demon discuss pride, distraction, resentment, social pressure, and self-deception as tools of temptation. The satire makes the moral dangers recognizable by describing them from the enemy’s perspective.

The book began as a series of pieces connected with Lewis’s wartime broadcasts and was later published by Geoffrey Bles. It became one of Lewis’s most widely read works.

Readers sometimes mistake Screwtape for the human target or for the main narrator of every event. He is the senior demon writing advice; Wormwood is the junior tempter receiving it.