Not including short story collections, poetry collections, anthologies, etc.
For me, I believe it’s Oroonoko by Aphra Behn because it was on the syllabus for three different classes that I took in college. Other than that, the most I’ve read a single book is twice, and that was Telegraph Avenue by Michael Chabon. I’ve read Dracula 1.5 times. Didn’t finish it the second time around.
I saw the movie in the theater when it came out. I was 16 and Michelle Pfeiffer, Winona Ryder, and Daniel Day Lewis were huge at the time. Teenage me loved the sets and costumes but I found the story boring and the subtlety went over my head. I rediscovered the book in my late 20s and fell in love.