LitCharts assigns a color and icon to each theme in The Book Thief, which you can use to track the themes throughout the work.
Death
Words and Language
Books
Stealing and Giving
Color, Beauty, and Ugliness
Summary
Analysis
Death resumes his musings. There are a few stories that he collects to distract himself from his work, and The Book Thief is one of these. When Death comes to Sydney to collect Liesel's soul, he takes a walk with her and shows her the book he save from Molching so long ago. Liesel is amazed, and she asks Death if he read it, and he says he read it many times. Liesel asks him if he understood it, but Death cannot answer. He wants to explain how mysterious he still finds humanity, especially that they could be both so good and evil, so beautiful and ugly, and their stories so "damning and brilliant" all at the same time, but he realizes that Liesel is already aware of all this. Instead Death states the only truth he knows to Liesel and the reader: "I am haunted by humans."
In some ways Death "stole" The Book Thief from Liesel, and now he is returning it – but like Liesel with Ilsa's books, the very fact that he took it shows how important it is to him. Death's final statement shows that humans are still a mystery to him, and he cannot understand how they can contain such contradictions within themselves and in their words. The strongest example of this is the evil of the Nazis and the goodness of people like Hans who put themselves in danger to help others, but also the use of language by Hitler to foster cruelty and evil as compared to its use by Max or Liesel to create art, beauty, and love, to bring people together. The word "haunted" implies that Death is still troubled by human nature, but it is also ironic because "haunted" is how many humans feel about death. Death turns the feeling back onto humanity, making us examine our own mysterious potential for both good and evil.