What is the name of C.S. Lewis's famous 1942 book written as letters from a demon?

C.S. Lewis’s 1942 book written as letters from a demon is The Screwtape Letters. The book presents correspondence from Screwtape, an experienced demon, to his inexperienced nephew Wormwood.

Screwtape advises Wormwood on how to tempt a human patient away from faith and moral awareness. Lewis creates an ironic perspective by making demonic advice expose habits such as distraction, self-deception, resentment, and spiritual complacency. The book is a work of Christian apologetics presented through satire.

Lewis initially published the letters in the Anglican newspaper The Guardian during 1941. The collected book appeared in 1942. Because the narrator is a demon, readers sometimes mistake the book’s advice for Lewis’s direct instructions; its method depends on reversing the viewpoint so that destructive ideas appear absurd or revealing.