Which C.S. Lewis book presents Christian ideas through fictional letters from a senior demon?

The Screwtape Letters presents Christian ideas through fictional letters from a senior demon.

Published in book form in 1942, The Screwtape Letters is structured as correspondence from Screwtape, an experienced demon, to his inexperienced nephew Wormwood. Screwtape advises Wormwood on how to tempt a human being and undermine his spiritual life. The unusual viewpoint lets Lewis examine pride, distraction, fear, vanity, and self-deception from an ironic angle.

Lewis wrote the work during the Second World War. The letters originally appeared in the Anglican newspaper The Guardian, which was edited by Lewis’s friend and fellow Christian writer Charles Williams. The book quickly became one of Lewis’s most popular works of Christian apologetics.

The title is sometimes confused with The Screwtape Proposes a Toast, a later speech and essay featuring the same demon. That piece was published separately in 1959. The original book is a complete sequence of letters, not a conventional narrative told by a human protagonist.