So pleased to hear that the finale was unexpected. I am sure that is the goal of a great many writer. It is also nice to see that you don't feel the research doesn't swamp the story. I read quite a bit in this genre and wanted to avoid some of the things that annoy me in those books. That meant, not too much preaching of history and no heroes (or villains) jumping out of aircraft and safely floating to earth aided by a handkerchief. Believable was my goal, so thank you for affirming that I pulled it off.
See you with my next book, working title 'Blind Run'.