Which 1942 book by C.S. Lewis presents correspondence from a senior demon?

C.S. Lewis’s 1942 book presenting correspondence from a senior demon is The Screwtape Letters. The fictional letters are written by Screwtape to his inexperienced nephew, Wormwood.

Screwtape advises Wormwood on how to tempt a human subject and prevent that person from becoming a Christian. Lewis reverses the usual viewpoint by describing spiritual and moral questions through the imagined bureaucracy of Hell. This satirical structure lets the book criticize vanity, distraction, self-deception, and shallow religious habits.

The work first appeared in serialized form in the Anglican newspaper The Guardian before being published as a book. Lewis later dedicated it to his friend J.R.R. Tolkien, though the two authors differed in their literary methods and religious writing.