Probably some recency bias but I'll go with Heart of Darkness, by Joseph Conrad. Soooo many people told me it's their least favorite book, and it's terrible to read, and I'm so glad I disregarded their opinion. They also called it racist which uhh, kinda misses the point.
I loved the book though. Psychological, philosophical, critique of colonialism and imperialism? A psychedelic descent into madness? Sign me up for more please.
In hindsight, it's absolutely something I would like, but my expectations were pretty low.