Back when you could make decent money on eBay for various offbeat but desirable paperbacks, you used to be able to get decent money for paperback reprints of the following:
Caldwell, Taylor. Dialogues With the Devil. Doubleday, 1967. First edition hardback, a Fine copy in a Fine- dust jacket with a slight bit of edgewear. Book in which Lucifer makes his case. Bought off eBay for $28 plus shipping.
Taylor Caldwell was a mid-20th century bestseller, but she isn’t read much anymore. She also wrote The Devil’s Advocate, set in a future communist dystopia, which also sounds like the sort of thing I should pick up.