Okay, I am fully prepared to be stoned for this next opinion but I'm not sure I classify ABC as a 'novel.' Is it a book? definitely. Is it literature? of course. Is it a novel per say? Probably not. 'Novel' is a categorization of form. It doesn't mean really long story told in book format (it's far different from epics or many forms preceding it.) but rather was an invention of the 18th century that was at first designed to categorize the life of a person. Early novels (think Tom Jones, Pamela, or countless other books that are exasperating to read) try to say EVERYTHING of significance about an ordinary person's life. Graphic novels are entirely legitimate -- I just think it's a separate form. They notable feature pictures with limited text, often involve the supernatural and/or the absurd, anthropomorphic animals, etc. The facts are they are different from novels; it's just a different genre.
As for children's literature I'm not sure whether or not it fits. Yes, a child can enjoy it but so can an adult. I hate the idea of children's literature being just badly written. I went to a reading at the box store earlier this quarter and it was someone who had started to write an adult novel but was told to turn it into a children's novel. It was honestly somewhat painful to listen to. Perhaps it wasn't complex/good enough for an adult audience? I hate the idea that young adult literature is just the rejects of the adult world but if that's what it does mean, this is not young adult's literature.
In terms of events described I feel graphic novels are often closer in length to a novella. This creates, as Chade describes a tremendous economy of words, most of which is dialog. Words are carefully chosen and no sentence must be so heavy that it drags down the weight of the story -- Gene Yang is great with that.
One other facet of the graphic novel/ comics is how wonderfully it portrays pauses. In stories you can say "he paused, leave a blank space, or try to describe exactly how empty it was but none of that works as well as a panel noticeably without speech/words. (See 98, 125, 137, 145 for some awesome examples). Loneliness as the absence of words? Poetic. Which makes it a wonderful medium for showing the loneliness of adolescence particularly in this setting. For that, and other reasons, it would be hard to tell this story in other formats.
Fantasy certainly has its place in novels but I think it's almost more easily accepted in graphic novels. Maybe that's from childhood connotations of cartoons and illustrations? I'm not sure, but I'm not surprised when I begin with a monkey. I think I'd be distrustful of the ending if this were told in another form. As is, it seems natural and right. I didn't see the ending coming but surprise endings (especially dealing with secret identities harking back to old superhero comics) seem natural to the form.
I'm not really sure what I ended up saying here but I really like Yang's work and I feel it fits better here than in another genre.
I also love the way exaggeration works so well in graphic novels. Things like a laugh track that can drive you nuts in sitcoms works really well to set the environment in Yang's work.
Also, two graphic novels that are kind of cool:
In Inverloch the character development is somewhat weak but the art is really awesome. (Especially when you consider that the artist did this for free online at first and only recently got published.)
I couldn't find an online version/sample of We3 but it's a pretty awesome graphic novel about animals in robot-suits. I find it hard to explain but it has a lot of interesting themes of loyalty, the harms of technology without a conscious, and just makes you think.