What are some of the main themes explored in Art Spiegelman's graphic novel, 'Maus'?

Maus is an iconic graphic novel by Art Spiegelman that chronicles the tale of Vladek Spiegelman, a Jew who survived Nazi Germany. Vladek is Art Spiegelman's father, and the story is narrated by Art as Vladek tells him his story.
The book can be considered a historical memoir, and many of the themes in the book lean on history to derive meaning. The tale not only tells Vladek's story, but also the story of the father-son relationship between Art and Vladek. Spiegelman uses historical plot structures of World War Two history and the father-son relationship to craft a few main themes throughout the work.
 
Alienation between humans; Racism
With much of the story set in Nazi Germany, it is not surprising that racism is a central theme in Maus. Spiegelman anthropomorphizes various animals to represent different ethnic races. For example, people of German descent are drawn as cats, those of Polish descent are drawn as pigs, and those of Jewish descent are drawn as mice. This representation is a tool Spiegelman uses to show the fundamental lack of understanding between humans during that time. Though in reality humans are all in the same species (homo sapiens), he draws them as entirely different creatures. Spiegelman's choice to draw his characters this way demonstrates the distance that opened between different ethnic groups during WWII as a result of the Nazi regime. 
 
Intergenerational familial misunderstanding
Throughout the novel, Vladek's story pauses and readers get a glimpse into the relationship between Art and Vladek. Often fraught with tension and disagreement, their relationship is frequently one of conflict. This narrative tension is juxtaposed with the very basis of the book: Art is choosing to write his father's story and clearly loves his father. Despite Art's deep love for his father, misunderstanding remains between them.
 
The interplay of memory and guilt
Two important characters die in Maus. Anya, Vladek's wife, and Richieu, Vladek and Anya's first son. Both of these characters ground Vladek's entire narrative. Within Vladek's story in Germany, they motivate and give him hope throughout his suffering in Nazi concentration camps. Later, as Vladek tells Art his story, they are conspicuously absent.  Both Vladek and Art suffer tremendous guilt over the death of these two family members. Both Anya and Richieu died due the Nazi regime and its repercussions. Art and Vladek did not cause their deaths, but still feel guilty. The particular kind of guilt they feel may be categorized as a type of survivor's guilt for making it through while their family members did not.