So my eldest son, who is eight, loves reading biographies. But most of the biographies he checks out from the library are in manga form. He's read about John F Kennedy, Babe Ruth and Honda founder Soichiro Honda -- all in manga form.
Since he loves cars, he really, really liked reading about Soichiro Honda. The manga actually taught him a lot about engines and how they work. It's a shame that some people look at comic books and somehow think they can't be educational or intelligent.