That's a nice little dinosaur review site there. Bookmarked for later.
I'll definitely agree with a lot of people's lists so far, so I'll add different ones mostly. First, I have loved Terry Pratchett's discworld books that Kitteh mentioned, and Guards! Guards! Is a good place to start reading!
Ranger's Apprentice is now a long running young adult series that might interest an 11 year old as it did me at the time. It's about an orphan learning to become a ranger (archer, rogue, survivalist, and king's secret service rolled into one) in a close to historic setting. Brotherband Chronicles from the same author is also good and follows a crew of young Nordic raider types who want to prove themselves.
I also wanted to contribute a warning that Dinosaur Lords has an amazing cover, but I found the book incredibly dry without considering the usefulness or hardships of owning and using dinosaurs in war or everyday life. The author would rather deal in medieval political intrigue at least in the first book. Also definitely not for younger folks, it has some negative graphic scenes.