What was the title of C.S. Lewis’s 1942 novel told through letters from a senior demon?

C.S. Lewis’s 1942 novel told through letters from a senior demon is The Screwtape Letters.

The book consists of correspondence from Screwtape, an experienced tempter, to his younger nephew Wormwood. Their letters discuss how to influence a human patient through distraction, vanity, resentment, and self-deception. The format lets Lewis present moral and theological observations from an intentionally inverted viewpoint.

Lewis dedicated the book to his friend J.R.R. Tolkien, although the two writers did not always share the same opinion of it. Lewis later said that writing in the voice of Screwtape became unpleasant because he had to keep his attention focused on evil.

The book first appeared in serial form in the Anglican newspaper The Guardian before being published as a volume. Its epistolary structure remains one of its most distinctive features.