Actually first read Hobbit/LOTR at 15 coz I was a big Led Zeppelin fan, and I'd heard some of their songs were based on the books. Once I started, I couldn't stop.
Have only read it (almost) 4 times, because I enjoy it so much, it makes me sad when I finish. (Actually in my latest [4th] reading -- started after "Fellowship" movie came out -- I've been on the "Many Partings" chapter for about 6 months now ... still can't bring myself to finish it!!!
I am one who never thought they could make a movie that would do the books justice ... but was very pleasantly surprised by the movie (even tho they did change some things!!)