I think that one of the most dominant themes in the work is the idea of how to assess guilt in a historical and personal setting. The Holocaust serves as the backdrop in which Hanna and Michael both struggle with moral and legal forms of guilt. Germany, as a whole, is shown to be struggling with the issue of guilt for its role in the Holocaust. The novel does not present anything simplistic. Guilt and the assigning of blame is shown to be incredibly difficult on both moral and legal fronts. When Hanna asks the courtroom, and essentially "the reader," "What would you have done," it is a moral query that strikes at the heart of all consciousness. In the end, many people would have complied like Hanna and have remained silent in the gallery like Michael. Guilt is shown to be difficult, complex, and intricate in multiple domains. This is one of the most dominant themes in the novel.
Another theme that emerges from the novel is one related to class tensions. Hanna has to take the job with the Nazis because she needs money. Her inability to read in a society that frowns upon illiteracy, but yet does nothing to eliminate it is reflective of economic reality. Hanna is ashamed of her condition in being illiterate. Yet, it is a condition that is brought on, in part, by an economic system that does little to ensure that all of its members can engage in the most basic of academic tasks. Michael and his father belong to a different class of people who can reflect, think, and pose philosophical questions because they have the economic means to do so. Class differences and acquisition of knowledge are shown to be connected to one another. This theme adds an even sadder dimension to Hanna's narrative.