I've started this review several times, and I can't seem to find the words to describe Maus' impact on me personally, and the impact it had on the graphic novel as art. It tells an important story, but its power comes from how the story is told; it wouldn't be nearly as effective as a simple prose novel.
Art Spiegelman (one of the artists who brought us Garbage Pail Kids; true story) tells the story of his father Vladek's experience during the holocaust using an effective visual metaphor: Jews are mice; Germans are cats. Americans, when they appear, are dogs. Admittedly, the metaphor breaks down the further you get from the source material (Spiegelman himself admits this in the text; cutaways to the present sometimes show him wearing a mouse mask), but it clearly illustrates the imbalance of power that typified the Holocaust.
The visual style is simple but bold. Thick black lines lend a starkness to the work that evokes the bleakness of Vladek's experiences. The characters are drawn simply, with an economy of line that adds to their humanity rather than distracts from it; the simpler they are drawn, the more of themselves the readers can project onto the maus protagonists.
Spiegelman tells his father's story simply, beautifully, and honestly. Despite the metaphors (or perhaps because of them) he masterfully captures the raw humanity of the players on both sides of the story, and deftly shows that even though portrayed as a metaphor of cat and mouse writ large, the protagonists and antagonists alike are still terrifyingly human.