M.P.
I read once that reading has to "click" for a person. All of the sudden you will understand how to do it and it will make sense. We all "click" at different times. Some much earlier and some later. It could be that he just hasn't had this happen yet. This article also went on to say that early readers and late readers would all even out in about the third grade with none having an advantage.
Last year my son could theoretically read (could sound out words) but I didn't think that it had really clicked yet for him. He absolutely hated to do it with me and would really complain. About halfway thorugh the year all the sudden he was OK with it. He came light years in a really short time. He still is not the avid reader my 9 yo is but he doesn't pitch a fit like he used to. He just doesn't enjoy it very much.
Another thing to keep in mind that many of the books for this age are geared for little girls. They are boring to boys. Try to seek out books that are a little more edgy. My younger son liked comics nuch better than books.