Which C.S. Lewis book is a fictional letter from a senior demon to a junior tempter?

The Screwtape Letters is C.S. Lewis’s book of fictional advice from a senior demon to a junior tempter.

The senior demon, Screwtape, writes letters to his nephew Wormwood, who is assigned to influence a human subject. The letters reverse ordinary moral instruction by presenting temptation and spiritual confusion from the viewpoint of Hell.

Lewis first published the work in book form in 1942. The unusual epistolary structure allowed him to satirize human habits, self-deception, pride, distraction, and rationalization while discussing Christian moral concerns.

Readers sometimes confuse the book with The Great Divorce, another imaginative work about the afterlife, or with The Problem of Pain, a direct nonfiction discussion of suffering. The Screwtape Letters is distinctive because its entire argument is delivered through correspondence between demons.