Which C.S. Lewis book consists of letters from a senior demon advising a junior tempter?

C.S. Lewis’s book consisting of letters from a senior demon advising a junior tempter is The Screwtape Letters.

Lewis published the work in book form in 1942. It is presented as correspondence from Screwtape, an experienced demon, to his nephew Wormwood, who is assigned to tempt a human known as “the Patient.” The fictional letters reverse ordinary advice: spiritual virtues appear dangerous to the demons, while distraction, vanity, and resentment are treated as useful tools.

The book began as a series of pieces published in the Anglican newspaper The Guardian. Lewis later dedicated it to his friend J.R.R. Tolkien, although Tolkien disliked the work’s format and subject matter. A common mix-up is to identify it as a conventional novel; its epistolary structure makes it a satirical theological work rather than a straightforward narrative.