I'll reread a book if I really like it or think there might be something I've missed. Like Dante, reread him every year, and read the novel Snow Country every now and then because I love it. Also, Catullus and Virgil - reread them every now and then both because I like them and to keep my Latin up to scratch.
I tend to reread Terry Pratchett every 10 years or so. He has a very neat way of cramming an idea into very few words and giving it a humorous twist.
I sometimes reread books as I get older that have made a significant impression on me when I was younger to see if I find them as fascinating. I tend to find them more fascinating. I must have re-read the Winnie the Pooh tales at least ten times since I read them first at 8. I remember also being fascinated with Alexandre Dumas (Sr) when I was a young child and reread everything he wrote at least once (The Three Musketeers -- I reread that six times) -- translated to either Russian or English, unfortunately. I am rereading Hitchhiker's Guide to the Galaxy right now for the sentence structure and punchlines (and for fun). I often find myself re-reading Shakespeare, especially A Midsummer Night's Dream, for the characters and to slow down when life gets too hectic. Rereading Poe, especially "The Cask of Amontillado," is now an annual family Halloween tradition -- my seven year old's been forevermore infected with Poe-isms.
I have, literally, worn out books by Heinlein, Michener, Clavell, Evanovich, and Uris, all from the number of times I read them. Dixon would be in the list because we had an entire set of the Hardy Boys in hardback (purchased at auction for, I think, a dollar), and those books were all I had until I was old enough to get a library card. Why? Because I learn from, and am entertained by, them.
My brother and I read every Hardy Boys book we could get our hands on back in the 1950s and '60s. I learned later that Dixon was a pen name used by a variety of different authors who wrote the series. Fascinating background story there, and a reminder that even hack writers had to earn a living somehow.