How does this comic book style account of the holocust maintain the level of seriousness appropriate to the topic?

While this seems comic book like, it is a true graphic novel in which the various classes of people are portrayed by animals. The horror of the Holocaust is shown through the animals, the way they are dressed, and the various ruthless ways in which the characters behave. The horrid Nazi "cats" are vicious as they treat the Jewish "mice" to the atrocities that we know happened in the various concentration camps during World War II. The story, which tells a tale which was related to Spiegelman by his father, is an accounting which shows horror and helps a young man understand the family history to which he must try to relate.