What is the title of C.S. Lewis's 1942 Christian apologetics book written as demonic letters?

The Screwtape Letters is C.S. Lewis’s 1942 Christian apologetics book written as letters from a senior demon. Screwtape, an experienced tempter, advises his junior nephew Wormwood about undermining a human patient’s faith and character.

Lewis presents the advice ironically: the demons’ language reveals the destructive habits they want to cultivate, including distraction, vanity, resentment, and self-deception. The book’s imaginative form lets Lewis discuss Christian moral psychology without presenting the material as a conventional theological treatise.

The letters first appeared in the Anglican newspaper The Guardian, beginning in May 1941, and were later collected as a book. Lewis dedicated the volume to J.R.R. Tolkien, though the book is not a collaborative work. Its epistolary structure and satirical voice make it one of Lewis’s most distinctive nonfiction publications.