This is Exhibit A in the case for adults reading YA. Like The Hunger Games, there's no wincing away from the horrors of war. There's a little bit of romance, but as in Rosamund Pilcher's The Shell Seekers or Coming Home, (which were not published as YA, but as women's fiction), the narrative remains focused on a young woman in wartime, and how that particular war dragged on so long that individuals held many different kinds of jobs and faced different kinds of hardships at different stages
History fans will love the depth of research Cooper did, and all the snippets of real characters and events that are incorporated. Devoted readers will enjoy that Sophie mentions what she's reading from time to time. Progressives and conservatives will appreciate that period characters express a broad range of ideals and are treated appropriately by the society of the day.
But I love it because even though Cooper allows her characters to discover all the worst atrocities, she also allows them to discover strengths within themselves, and to find a way through. The villains don't always get punished, but the good do receive some sort of reward, if only the relief of it all being over.
Library copy.