The story has two main threads. The first is the true story of Holocaust survivor Vladek Spiegelman's experiences as a young Jewish man during the horrors leading up to and including his confinement in Auschwitz. The second intertwining story is about Vladek as an old man, recounting his history to his son Art, the author of the book, and the complicated relationship between the two of them. It's a difficult process for both father and son, as Vladek tries to make sense of his twighlight years, indelibly marked by his experiences and a slave to the processes he had to resort to in order to make it through. On this level, it's also about Art, as he comes to terms with what his father went through, while still finding the more irritating aspects of his father's personality difficult to live with.
Maus uses anthropomorphic characters, using different species of animal to represent the different characters' race or nationality - Jews are mice, Germans are cats, Americans are dogs and the Polish are pigs. This doesn't always quite work, though Spiegleman is acutely aware of this as he struggles with whether or not to make his French wife, converted to Judaism before they got married, into a mouse or some other species. Please don't instantly dismiss this as childish nonsense though - it owes more to Animal Farm than Mickey Mouse.
It's a sad tale, as although Vladek survives the Holocaust, the shadow of the great swathe of humanity that was butchered by the Nazi killing factories hangs over the entire book. It is also haunted by the ghosts of Vladek's first wife Anja and their son Richieu; the former surviving Auchwitz but eventually committing suicide, the latter not making it out of Poland.
This book, originally a two volume work is now...