The slice of life manga at its best. Fusing comedy, romance, and no small amount of baseball Adachi creates a grand story of quiet intensity. While Adachi does add in some very corny jokes every now and then, the humor stays fresh throughout the series, even in the presence of the powerful emotions of his well developed characters. The character design does seem to be of an older style, but looks new and works perfectly with the story; combined with detailed backgrounds, the art gets an A+. You DO NOT have to like baseball to enjoy this manga thoroughly. I had decided that baseball wasn't cool. After reading Cross Game, my attitude made a 180 turn and I now consider myself as big a fan as any. Cross Game is perhaps my favorite manga, and I only say perhaps because it's hard to compare manga of completely different genres.
In short: it's really really good for all ages. You should read it.