I reread a lot, as I talked about when I wrote a post about Walter Mosley. People experience works of music more than once, why not books?
When I was into Inherent Vice (a period of about five months, during which I blogged about it many times) I read and reread the book, plus I listened many times to the excellent audio version (read by Ron McLarty). Plus posting on the Pynchonwiki, and reading all the other posts there.
Some things I reread are for “comfort reading” reasons, but that’s usually different. As Theresa says, that’s much more likely to be dipping in to read favorite parts. But when I’m rereading to study and learn, I always read the whole thing, from beginning to end. Which is not to say that it’s all dry, academic analysis; there is a particular pleasure in understanding something really well.
I don’t read books about writing. I’m not opposed to it on principle, but for me I’d rather read great books, again and again if necessary, and learn what I can from them.
I also reread my own stuff from time to time, to see what I think about it from a different perspective – where I did well and where I could have done better. Not to rewrite (when a book is done, it’s done), but to apply the lessons to what I’m writing now.
I rewatch movies, too. Some of my reviews are of movies I’ve been watching and thinking about for decades – and if I have anything interesting to say it was it was those decades that made it possible. The most amazing thing to me about Roger Ebert was not that he wrote so many great and interesting reviews, it’s that he wrote at least most of them after having seen the film exactly once. I don’t even see how that’s possible.
(And yes, most of my music listening time for this year has been spent with Les Miserables – the 25th anniversary concert version as I write this.)