Which C.S. Lewis book presents a series of fictional letters from a demon to his nephew?

The Screwtape Letters presents fictional letters from a demon to his nephew.

Published in book form in 1942, The Screwtape Letters consists of correspondence from the senior demon Screwtape to his inexperienced nephew Wormwood. The letters offer advice on tempting a human patient, allowing Lewis to examine habits, self-deception, distraction, pride, and spiritual complacency from an intentionally reversed perspective.

The book began as a series of letters published in the Anglican newspaper The Guardian in 1941. Lewis later collected and revised them for publication. Its satirical format makes the work distinctive among Lewis’s writings, but it is not a handbook of demonology or a literal theological document. The fictional demon narrator is designed to expose temptation by making destructive advice sound practical and reasonable.