Many years ago, I read Umberto Eco's the Name of the Rose and Foucault's Pendulum.
Foucault's Pendulum is based on a delightful conceit, that all conspiracy theories are ultimately true because they become self-fulfilling prophecies. Indeed if you start looking into the history of various intelligence operations, you quickly come upon real life examples of the kind of nutty characters you thought existed only in an Umberto Eco book. And not just intelligence operations, also at Bell Labs and the Jet Propulsion Institute:
https://www.wired.com/story/jpl-jack-parsons/
The Name of the Rose I found engaging but ultimately too polemical concerning the backwardness of the European Middle Ages. At the time time, I was working as a cataloguer in a medieval microfiche library, which had a very large and broad collection. I assure you medieval man was more concerned about the color of his piss and what it meant about his health than he was about the coming Apocalypse.
Any recommendations on Eco books, or something similar in spirit (erudite and witty even if lefty)?