Graphic novels can be a way to get someone to read at least. They can be fun for adults too. I've got a couple of Star Trek ones I need to pick up.
With Osprey the illustrations and facts should be pretty solid. I see them as junior's first military book. Easy to read, lots of pictures, and hopefully enough to keep a kid interested in history. I got hooked with a set of illustrated volumes of the History of the Americas. Mom got them with points at the grocery. I quickly claimed them. I was maybe 7 or 8. I can still see a illustration of an Aztec sacrifice. I built my first models the sames time. Still build models and still am still likely to be found in the military section of the bookstore. That first F-18 is wrecked but still on my desk and I pulled that rather worn set of books when I was researching a paper for my Trans-Mississippi Frontier class.