I haven't finished reading the novel yet, but I purchased it as a reference source--not as entertainment--so in that respect, it has been providing me with what I needed. Since the writing style is satisfactory, but has not inspired me to continue reading for any other reason (i.e., because I'm really enjoying the story or characters) I only gave it four stars. My standards are very high however, and generally speaking, I'm a guy who does not especially like reading novels. In my entire life, I have only read a handfull that I really enjoyed: A biography about Sam Houston, Désirée by Annemarie Selinko, The Forgotten Door by Alexander Key, Pride and Prejudice by Jane Austin and The Hunger Games by Suzanne Collins
While for the most part I enjoyed this book and the plot twist at the end was excellent the portrayal of American politicians was off putting. The authors own original characters were fresh and interesting while the American politicians were portrayed as cardboard, very shallow and irritating. There are plenty of ways to portray politicians making mistakes, that is after all the reality of the human condition. No need to make them caricatures to dismiss as buffoons.
On the plus side the book is a fast read, I finished it in 14 hours taking only modest breaks, and seeing fully developed complex characters who were Canadian was a rare treat in this sort of fiction. The science of how Tsar Bomba would actually work and the level of damage it would actually cause is grossly exaggerated, but I am willing to give that a free pass because it has become a cultural meme that nuclear weapons kill everything despite what real world testing and physics have shown to be the case.