Just finished The Exorcist (40th anniversary edition). Meh. Medically and religiously speaking, it's incredibly well researched, but the Father Karras character (a Jesuit psychiatrist) treats phenomena like mind-reading and telekinesis as facts of modern science, ruling them out as signs of Regan's possession. I'm glad those elements were left out of the movie. The prologue was a mess and the first few chapters didn't draw me in at all. The book was written in omniscient POV, with quite a bit of telling, and overuse of flashbacks. I don't mind omniscient if it's well done (e.g., Dune), but in this book, the author, William Peter Blatty, headhopped like a ping pong ball, including describing things that happen when no one is present to see them. Also, a heavy focus on excrement, vomit, and obscene masturbation involving Regan that took me out of the story. Nevertheless, none of the above got in the way of him selling 13 million copies, so what do I know? I got some useful research out of it, although I prefer the prequel, Exorcist: The Beginning, written by another author.
Now back to researching the Book of Revelation. I now have five books on interpreting Revelation, three of them written by Catholic theologians, and they all disagree wildly about the prophecies. One of the Catholic authors cites quack science about the ability of the U.S. government to use EMF-emitting technology to control our thoughts.