wrinkle in time (l'engle), and Matilda (roald dahl) although Matilda is not a boy!

Harry Potter if gifted in Magic counts, my kids started reading them at 5-6

I also want to say the Dark is Rising series, that's magic too. I think I was reading them at 7 but I may have forgotten.
http://en.wikipedia.org/wiki/The_Dark_Is_Rising_Sequence