R..
Yep...I was college level by fifth grade...I still LOVE to read.
like Marie C. said just because it was below my "level" I still enjoyed Judy Blume books, Nancy Drew, Encyclopedia Brown, tons of the "kids" classics.
I also was able to really appreciate the required reading material for each level. I read it quickly and got the point quickly but still it amazed me that others didn't "get the book".
I went to the public library once a week and was very close to my elementary, middle school and high school librarians even being aides for some of them.
Just find him books that he likes to read...my son reads several grades ahead of himself BUT when he grabs a book for fun, it is Diary of a Wimpy Kid or Calvin and Hobbs. The older favorites and younger reading levels...but he likes them.
For me fiction was fun reading no matter what the "level"...I had read all of Agatha Christie by six or seventh grade, but still loved those Nancy Drew.
The biggest advantage I had was doing non-fiction research I could read more and find out more on any given topic because I could understand it. I rocked science fair all the way through high school.
Let him have fun with it and enjoy reading!!