My DS now 8 was like this. He exhibited very little interest in reading really until first grade, but he absolutely loved to be read to from infancy. I have always been a great believer that one of my jobs as a parent is to teach my kids the joys of reading not just the mechanics of it. If I had tried to force him to read on his own, I don't think he would have enjoyed it. So I kept reading to him and just waited him out until his ability level crept closer to his comprehension level, which it eventually did. He always read at or slightly above grade level, but this year in second he just took off! I really think the exposure to more complex writing was a great benefit.
I say read the more complicated stuff to him because that is what his mind is craving. And he is gaining exposure to more complex ideas, plots, themes etc., which ultimately is the "harder" part of reading, so it will serve him well later on.
FWIW, I also am suspicious that he may have a visual-motor LD, but he compensates so well for it at this point that it is hard to say. But he still doesn't have a huge stamina.
