Which C.S. Lewis book was published in 1942 as a series of letters from a senior demon?

The Screwtape Letters was published by C.S. Lewis in 1942 as a series of letters from a senior demon. Screwtape writes to his junior nephew, Wormwood, about tempting a human subject.

The book uses satire to discuss Christian ethics, spiritual distraction, pride, repentance, and everyday habits. Because the advice comes from a demon, the reader must interpret the letters ironically: Screwtape’s goals are the reverse of the moral goals Lewis wants readers to recognize.

Lewis wrote the work during World War II, when he was also delivering radio talks that later contributed to Mere Christianity. The letters were first published in the Anglican newspaper The Guardian before appearing in book form.

The book is not a conventional narrative with a sequence of heroic adventures. Its epistolary structure gives readers a sustained fictional look at temptation from the enemy’s imagined viewpoint.