My mom recently forwarded me a New York Times editorial titled "Some Thoughts on the Pleasures of Being a Re-Reader." It's a great article and describes exactly how I feel about re-reading. The author talks about how many people brag about never reading the same book twice, desiring to always discover new information. But she says, "At heart, I’m a re-reader. The point of reading outward, widely, has always been to find the books I want to re-read and then to re-read them." I always make fun of my mother because she reads the same books over and over and over again. Your chances are pretty good if you guess that Maurice Walsh's And No Quarter or Susan Howatch's The Wonder Worker are on her bedside table. She has read some new stuff on my suggestion and I'm always very proud of myself if one of those books becomes a re-reading favorite (Jennifer Crusie's books are an example).
But I looooove to re-read too. It's so comforting to settle into a book that you know you're going to love, because you've loved it before. I've spend the last couple weeks re-reading Harry Potter numbers 6 and 7. (Number 6 so that I'm ready for the movie to come out, and 7 because I couldn't stop myself.) Then none of my new books really called to me, so I've started re-reading Sara Donati's Into the Wilderness books.
Occasionally I think that I shouldn't be wasting my precious summer re-reading old books -- I should be discovering new great books. But then I realize that I only have a limited time available to read for fun, so I'll do whatever gives me the most pleasure. And right now that's re-reading favorites. :)