I've read more than my share of WW2 books, but The Book Thief was probably the best I've ever read. It surprised me to find out that it is classified as young adult; while the protagonist is young, the level of writing and in particular the depth and moral ambiguity of the characters make it a worthy read for those who are well past adolescence. The plot is not always fast-paced, as we see Liesel grow up in a poor section of a German town, but it is enjoyable--Zusak's portrayal of children and young teenagers is the best I've seen in a long time, avoiding the common pitfalls of turning them into miniature adults on the one hand, or shallow caricatures of childhood on the other. In fact, by the end, the characters young and old will probably seem more real than a lot of the real people you know!
This is an amazing book, and one that steps outside of the box in many ways, even in addition to the choice of Death as a narrator--a choice that seems quite appropriate to the story, as Death has plenty of unique insights to offer without breaking the flow of the story. At times Zusak seems a bit heavy-handed with his themes (the humanity of the Jews in particular; do the few people out there who dispute this actually read mainstream WW2 novels?), but in my case this did nothing to detract from the overall experience. This is one of those few books that really will make you laugh and cry, and deals with a difficult time period without beating you down. Quite an achievement.