Which C.S. Lewis book is presented as the autobiography of a demon giving advice to a junior tempter?

The Screwtape Letters is C.S. Lewis's book presented as advice from a senior demon to a junior tempter.

Published in book form in 1942, the work consists of letters from Screwtape, an experienced tempter, to his nephew Wormwood. The senior demon explains how to influence a human subject away from faith and moral attention. Lewis uses the inverted viewpoint to expose temptation, pride, distraction, and self-deception.

The book began as a series of letters published in the Anglican newspaper The Guardian in 1941. Lewis later gathered them into a volume. Its satirical method means that readers must reverse the demons' values to understand the moral argument.

The Screwtape Letters is not an autobiography in the ordinary sense, despite its epistolary and personal tone. It is a fictional correspondence. Mere Christianity is a separate apologetic work, while The Great Divorce is a theological fantasy about a journey from hell.