I was a late bloomer, as far as reading went. I didn't feel the need as my intuitive rationale at the wee age of five was that it simply wasn't necessary; I can do what I want, function just fine without reading, so why waste time learning... ... then my mom brought home some comic books from the convenience store down the street, a Spider-Man and a Fantastic Four, and while I enjoyed the pictures, I really wanted to know what they were saying. The Fantastic Four had less exciting imagery yet an abundance of speech bubbles so I figured, these guys must be saying something important. This strongly motivated me to learn and I was reading rather large books by the age of 10 (my fifth grade teacher felt that that uncut version of Stephen King's The Stand was inappropriate at my age and was shocked, both positively and negatively, that I understood the context and ambiguities of certain scenes).
That all being said, it's my suggestion that you grab a stack of comics that range in terms of popularity, style and maturity and he'll be motivated by what he likes.
Perhaps check on eBay for used collections of comic books as they go cheap there. The classic comic books may have less violence and more of a moral high ground than current day comic books.