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.
About Lawrence Person
Lawrence Person is a science fiction writer living in Austin, Texas. His short fiction has appeared in Asimov's, Analog, Postscripts, Jim Baen's Universe, Fear, and several anthologies. He also edits the Hugo-nominated SF critical magazine Nova Express, and runs the Turkey City Writer's Workshop. His non-fiction has appeared in National Review, Reason, Whole Earth Review, The Freeman, The World & I, Science Fiction Eye, The New York Review of Science Fiction, and Slashdot.org. He owns such a large library (mostly science fiction first editions) he had to buy a two-story house to put it in, and then adopted a golden retriever to drag him out of his house on a regular basis. He also makes a mean batch of salsa.