I've read James Michener's Hawaii twice, and Alaska three times. Good books like good movies can be revisited. But my record of rereads is Bill Bryson's A Short History of Nearly Everything, which I have read too many times to possibly count. It's the only book that once when I finished the last page, I flipped back to the first page to begin reading again. After that I would pick it up from time to time and reread it. His style of writing flows so easily for me. It's like he's talking to me. In addition, that book has so much factual information written in such a light style, that I couldn't digest all of it in one read. I've read it maybe 10 times.
But this is weird, I bought copies of that book twice to send to friends, who never read it, or started, and put it down unfinished.