"I Killed Adolf Hitler", in addition to being fun to say, is a really good little graphic novel. It's quite short, which greatly limits it's ability to carry more complex feelings, but it does have enough time to transmit to the reader a sense of emptiness, loneliness, loyalty, and even tenderness. Like several other graphic novels, human form becomes animal form, perhaps in order to prevent the reader from judging or identifying with the characters quite so easily, or at least that's what I think the artists are (often unconsciously) doing, almost the opposite in reasoning to their use in "Maus".
This is a tiny little book that's easy to dismiss, but it's well worth it. I enjoyed it a great deal.