Is there more than one tone in Zusak's The Book Thief? Is it situational or character dependent?

First, the tone is the author's (or narrator's) attitude towards an individual subject or story. Zusak's The Book Thief revolves around World War II, so the tone is not a happy one for the most part, anyway. Next, the book is written from Death's perspective, whose voice automatically creates a dark and somber mood because he has a depressing job. Additionally, Death tells Liesel Meminger's story through witnessing her life and by using her journal as a source. Therefore, there are technically two narrators/characters telling the story. So, this fact adds to the question of whether there are two or more types of tone in the story. For the most part, though, the story recites the tragic events that face Leisel Meminger during the war. Fortunately, she does experience some happy moments. One theme might be that even though the world is at war, one can find a moment of peace and happiness once in awhile. For example, when the Hubermanns have a snowball fight with Max in their house, the following is shared:

"For a few minutes, they all forgot. There was no more yelling or calling out, but they could not contain the small snatches of laughter. They were only humans, playing in the snow, in a house" (312). 

Overall, though, a story about the tragedies of war generally creates an attitude of sadness and despair towards human kind. So I'd say that the tone can and does change in the novel based on different events that the characters experience. Since the characters all face the destruction and horrors of war, there is not just one who can change the tone or mood of the story; therefore, the tone changes as an event or situation changes.