It's quite a story. Gen's father is an anti-war pacifist, which makes the lives of Gen's family extra-difficult in 1945 Japan, where food is scarce and pro-war fervor dialed up to 11. For the first 200 pages or so of this first volume, we observe the food shortages and the petty injustices of state and individual alike.
As Art (Maus) Spiegleman notes in his introduction, some of the conventions of Japanese comics (Manga) take some getting accustomed to for the Western reader. The children are big-eyed cartoon kids. Cartooniness can shift suddenly to photo-realistic rendition, especially of machines and buildings, and back again. And there's a violent jokiness throughout, a heightened slapstick of punches and kicks directed mostly by Gen's father at Gen and his equally rebellious but well-meaning younger brother.
The occasional melodramatic jokiness of some of the proceedings doesn't obscure the smaller horrors of war, and the larger one, when it comes, is a stunner -- 50 pages of unrelieved horror, all set in the first few hours after the Bomb fell on Hiroshima. The nine subsequent volumes take Gen up to about 1947. This one should probably be on every serious comic reader's bookshelf. Highest recommendation.