Which C.S. Lewis book is a collection of letters supposedly written by a senior demon?

The Screwtape Letters is a collection of fictional letters written by a senior demon.

C.S. Lewis published The Screwtape Letters in book form in 1942. Its narrator, Screwtape, advises his inexperienced nephew Wormwood about tempting a human being. The letters present moral and spiritual dangers from the demons’ imagined perspective, allowing Lewis to use irony rather than direct instruction.

The book first appeared in the Anglican newspaper The Guardian, which published the letters during 1941. Lewis later dedicated the work to J.R.R. Tolkien, although the two writers differed in how they approached literary and theological subjects.

A common mistake is to describe the book as a literal account of supernatural correspondence. It is a work of imaginative Christian satire: the demonic viewpoint exposes pride, distraction, resentment, and self-deception in ordinary human life.