Well, we're on the second Mysterious Benedict Society book now, and DS7 enjoys them.
Some of the older classics that haven't been mentioned here (I think) are the Madeleine L'Engle books (Ring of Endless Light, etc.), the Black Stallion books, and Scott O'Dell (Island of the Blue Dolphins, etc.).
Some nonfiction books that he loves to death are "Why Pi", "Go Figure!", and the "M&M's Book of the Millenium". We check them out at the library, renew them, renew them again, return them, and then next trip check them out again and start over. We have these books for 9 out of every 12 weeks now! I was going to get them for him for Christmas, but I got the Mysterious Benedict Society and a Calvin and Hobbes instead.