For me for example its “Eat me - a natural and unnatural history of cannibalism” by Bill Schutt. Its an amazing book that covers cannibalism in animals and then the history of it in humans (cultural, survival & medicinal cannibalism).
I got a lot of “oh why would someone read something like that?” And “that not something fun to read about!” From relatives but my friends enjoyed the stuff that I could tell them about cannibalism!
Probably "The Illuminatus! Trilogy. 1970’s era anarchist fiction that tries to link every conspiracy (of the times) to, eventually, a rock concert in Switzerland with occult-ish consequences.