This book was an ENIGMA! The puzzles were intriguing. The plot kept me spinning around in circles trying to figure out what was going on! It was definitely on the edge of your seat suspenseful. It conveyed the feeling of being lost, both physically and emotionally well. It was actually a bit confusing, but I’m wondering if that was intentional to make the reader feel as the characters felt. This one was a puzzle indeed. It’s hard to know exactly how I felt about it. I’d give it a 3.5, even though half stars aren’t really a thing.

At first, having finished this novel, I thought I was let down. As an adult, I still think I am, because I wanted more inside the universe of this novel, more connecting the various twists in plot. But I think this is one of the most beautiful middle grade books I've read in a while, introducing readers to the format of mystery, human tragedy, and the two world wars in an easily digestible format.

History and science mix to make this an interesting story! Great for kids who have a scientific mind and love codes and puzzles!