Mind, I actually think the ugliness of the art serves to underscore the ugliness of the story: It's a kind of Stylistic Suck if you will. It wouldn't be half as effective if it used glossy art and beautiful people.
I think Watchmen is something of the same (it uses a lot of secondary colours for instance, which often makes it look like raw liver, but makes it very distinct, the movie totally missed the train on that one)