Is it possible he has a visual challenge? This sometimes seems to be the issue with good readers who are relucant to read themselves, but prefer to be read to.
I guess my point about "Boys like..." is that while I certainly think it's fine to offer nonfiction and Capt Underpants, etc, I wouldn't get into the mindset that it's pointless to offer other diverse chapter fiction to boys. It may just take a while to hit on the right thing, or sometimes it's a maturity issues. DD has a friend who was not interested in reading really at all till about age 8, but now he's a major fiction buff. They kept reading aloud and kept trying different things, and actually it was Harry Potter that clicked.
I agree, I was just saying (since she was comparing her DD and DS) it's not unusual for boys to not as interested in fiction or chapter books so she could try more nonfiction if she hasn't already.