Volume two of "Barefoot Gen" follows Gen from directly after the bombing of Hiroshima to what would seem to be a few days later. The scenes of the devastation and suffering in Hiroshima are very moving. And the general shortage of practically everything has pretty much reduced everyone to a grim struggle just to get by. For the most part, everyone that Gen encounters has either been horribly maimed by the bomb, lost most of their family, or is only concerned with their own survival and has no intention of helping anyone else. This may be an accurate portrayal of what Hiroshima was like at that point, but that doesn't keep it from getting sort of old after a while - or maybe, fairly quickly.
Nakazawa's drawing is adequate for the purpose of telling the story, but I think it's fair to say that no one ever read his books for the fantastic art. Presumably, if you're reading the series, it's because you're interested in the subject matter, and for at least the first two volumes of the saga, that's been enough to carry the story. But I have to say that Nakazawa's experience as a Hiroshima survivor gave him an interesting story to tell, but in his telling it, neither his plotting nor his drawing rises above a level I'd call crude.