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!
The first thing that came to mind was one of my favourite reads of the year - Dark Archives: a Librarian’s Investigation into the Science and History of Books Bound in Human Skin by Megan Rosenbloom. I love anything esoteric and I love books, so this was the perfect crossover for me.