This author, who also wrote Hitler's Secret, has a great feel for this time period. There are very few books that show people who "sympathized" with the Nazis because they preferred that course of action to death. I think that many people took that route; I had a friend who was in the Wehrmacht even though his home in Polish Silesia was taken over by the Nazis. He felt that he didn't have any other choice, and it's nice to see a literary character faced with the same conundrum.
Certainly, the Nazis are not portrayed as good in any way, and I liked how Osborne took little known historical facts and wove them into his story. There's plenty of action (including flying around in planes!) to suit readers who like to read about the fighting in WWII, as well as Tygo's suffering.
The cover earns additional points for historical accuracy-- I love that this is a photograph, but the boy and girl are wearing clothing that looks really on point to me!