T.W.
Well, when he starts to read he wont be reading chapter books.
Some good beginner books are Berenstein Bears, Mercer Meyer, and Dr. Seauss. My kids loved those and both learned to read with them--then in first grade they began reading simple chapter books like Junnie B Jones,captain Underpants and Magic Tree house.
A nice series for you to read to him now or him to read later is Michigan and American Chillers.