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.
The Princess Bride. I first read it to myself, then I read it to a boyfriend many years ago and more recently I read it to my child. The next would be Stardust which I first read several years ago and then read to my child a few years ago.