In her "Author's Note", Larson says that she began writing this story during the Iraq War, and that she could see similarities between the World War I Era and that of the Iraq War. Patriotic fervor, distrust (or outright hatred) of foreigners, the "liberty cabbage" (sauerkraut) of 1918 and the "freedom fries" of 2003. And it was interesting to read the book in 2016, with some of the same themes prevailing.
Although I found it in our library's Young Adult section, the book reads at more of a junior high or middle school level to me. That's not to say it wasn't a good read; I enjoyed it, but the language and the themes seemed geared toward a younger audience.