* AlternativeCharacterInterpretation: How much of Screwtape's advice to Wormwood is genuinely meant to help him, and how much is it an attempt to set him up for failure?
* {{Anvilicious}}: The story is very clear about Lewis' beliefs, posing that every thought and action taking you away from God is product of a devil subtly whispering in your ear. It must be noted that Lewis, a former atheist, based Screwtape's modus operandi in his own personal temptations.
* EvilIsCool: Averting this is pretty much the whole point, as C.S Lewis was aware of this trope. Not only is Screwtape himself a stuck-up member of Hell's middle management and a cranky {{Jerkass}} with no sense of humor, but he gives tips to Wormwood on how to minimize how much The Patient can enjoy sinning.
--> And anyway, why ''should'' the creature be happy?!
* FanficFuel: The format inspired quite a few people to try and write letters from Screwtape tackling issues they care about. Most don't quite have the same charm as the original.
* HardToAdaptWork: Despite many adaptations that have been made over the years, in [[WordOfGod C. S. Lewis's own opinion]], the book was inherently unstageable and unfilmable, and he turned down several requests for permission to adapt it. It's not hard to see his point, considering the book is an EpistolaryNovel from the point of view of an UnreliableNarrator, and any plot arc is mostly incidental to Screwtape's essays on moral philosophy. One author pitched Lewis a script that used a FramingDevice; Lewis's advice was that the framing story would work so much better on stage that the author should just go ahead and make it into its own play, leaving Screwtape out of it!
* ParanoiaFuel: The book suggests that every thought of a human being may be influenced and corrupted by demons so as to turn them away from God, even those thoughts which are religious in nature. Even those who think they are repenting may actually be doing no such thing.
* ValuesResonance: Many of Lewis’ comments have aged incredibly well. For example, gluttons like the Patient's mother (an [[ObnoxiousEntitledHousewife obnoxious]] and demanding UnsatisfiableCustomer) are still sowing pain and discontent today. Other examples include preaching how science and religion can and should coexist, pointing out corruption in churches, criticizing human pettiness, and examining subtle but dangerous forms of lust.
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