I think Blundell's book deserved the National Book Award for many reasons, but most notably for it's sensitive handling of mature subject matter. Without shoving it down our throats, she gives us a character who just doesn't see how one can discriminate against Jews for no real reason, which can be helpful for younger readers who need an "ally" (fictional or not) in sticking up for others. Additionally, she gives us a very flawed family and shows how parents are humans, too. I think that this realization is one of the key parts of adolescence - the time between "My mom is stupid and always wrong!" in middle school to "My mom is human and sometimes she is wrong, but she is my mother" as you grow older. Her character chooses to keep the family together by lying despite her anger at her mother and suspicion of her stepfather, but does it in such a way that a reader can form their own opinion of what she should have done.
Despite the heavy topics (infidelity, sexuality, war, anti-Semitism) Blundell's book also includes many of the things a teen girl worries about in a relatable way... so that maybe even a girl who doesn't aspire to smoke cigarettes glamorously can relate in the way that she aspires to listen to music in coffee shops alone. The plot is intricate and detailed, and while I felt the characters could have been developed more, I liked her approach because it allowed me to relate them to people I knew and better visualize them despite the difference in time period.