For some reason, I can't bring myself to re-read a book. I don't know what it is, but whenever I try, I find myself remembering what happens later and it ruins the experience for me, so I don't finish.
I don't seem to have this problem when I watch reruns of TV shows like Star Trek: The Next Generation or Charmed, for example. I'll sit down and watch an episode that I've seen three, four, five, or even more times, no problem.
Is it detail? When one watches a TV show, one can't slow down or rewatch (TiVo, etc excluded, but you know what I mean) scenes to pick up on details. You're at the episode director's mercy. With a book, however, no scenes rush by, no detail passes your notice. If you do miss something, you can easily flip back a few pages to re-read the pertinent information.
I guess this is why I can watch reruns but I can't re-read. Each time I rewatch an episode of a TV show, there's always a new detail to notice, a joke to finally notice. Re-reading a book just doesn't have the same sense of new-ness.