Spoiler alert: This post is part of an in-depth discussion of Perelandra by C. S. Lewis, which will inevitably reveal key plot points. I recommend you support your local bookseller or public library, and read the book first.
Philologist Elwin Ransom, brought to the planet Perelandra (Venus) by Oyarsa, the spiritual ruler of Malacandra (Mars), encountered his old enemy Weston who had abducted him to Malacandra, while exploring Perelandra's sole fixed island with the Green Lady, the planet's only woman. Weston's personality is gone: Ransom believed he had become an Un-Man, an animated corpse possessed by the malevolent spirit Weston had called the Force, but which Ransom believed to be one of Satan's allies, if not Satan himself.
Ransom later found the Un-Man by following a trail of tortured animals. He was trying to tempt the Green Lady, into violating the one law decreed by Maleldil, the ruler of the universe: not to live or spend the night on the island. After Ransom dissuaded the Lady from listening to the Weston-thing, that was Weston, it engaged in psychological torture on him, calling his name for no reason to keep him awake all night.
Typically, I use September to broaden my literary horizons a bit: try something I've never read before or wouldn't pick up on impulse. This year, I've decided to keep it simple: get through William L. Shirer's The Rise and Fall of the Third Reich. It's a classic work of World War II history that weighs approximately one anvil. I've owned my paperback copy for somewhat over 20 years and never read more than the first few chapters.