Well written and I loved learning about new aspects of the war like Guernica. And I love a good spy story, of course. 

I thought the book did a great job at weaving in various major occurrences of Nazi German like intense propaganda, removing children with disabilities from homes, blackmail, and the rocket program. The conflict Sibi felt but realistic and purposeful approach she took were difficult but relatable, as you put yourself in her shoes. I loved her tenacity and determination to use her situation and take back control that the Nazis continually took from her. 

Really well done and hard to put down.