I guess my question is 'how do you know that the material is over his head?'
If the language is beautiful and the characters are compelling, then your son probably gets the same thing out of reading the books that other people get.
I was reading about the lexiles, and how they recommend that a child read at about 75% of their highest ability. That seemed so weird to me. I think it's individual, but I always 'got' everything that there was to get in a book the first read through. I know of other people who report seeing so much more on the 2nd or 3rd read, so I know that my experience isn't universal.
Now it's true that as my life experience develops, I identify more strongly, or differently with different aspects of the book. One example that you might enjoy reading with your son, is 'Ender's Game' - when I read it as an adult with my son, I had a lot more feelings about the shadowy parental figures. I've read interviews with OSC that the same thing happened to him, and that in the later books he has developed the parents more fully - and I've enjoyed noticing that as well.
I don't think that parents need to assist their children with reading as much as be an active discussion partner. That's what I remember missing anyway as a child. I seemed to almost inhabit the books and then was quite lonely with no one to discuss them with. Plus, by reading books together one builds a family vocabulary with references and in-jokes, which I really enjoyed with my son. There are moments when we just look at each other and know that we are both thinking of the same literary reference. And we grin.
Love and more Love,
Grinity
