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 don’t reread books a lot anymore for time reasons. Even if I like a book, I usually go digging into the authors body of work. Books that do get a reread also get a spot on my personal book shelf.
But then there’s the Percy Jackson series, esp volume 1 – it’s just comforting and sometimes I need to conjure the illusions of safety I had as a kid. Life is rough, but then there’s this nostalgic and affirming book of victories over fictionalized mythological monsters. I’ve lost track of how many times I reread this tbh.