Macadam also has the tendency to lay it on a bit thick. “This was not a dystopian society created by some novelist,” she writes at one point. “Auschwitz was a real-life Hunger Games.” She is right, of course, but at times the tragedy of the girls’ fates is undermined by the mawkishness of her writing. While the Slovakian girls were enduring hell on earth, their families were wondering what could have happened to them. The book includes very moving postcards sent to the camps from worried relatives, which attest above all to how little was known about what was really going on.