This was really good, with a lot more to it than you usually find in the books in this series. It captures your attention as the h, Kristin discovers she truly has married a man of mystery, but what will she find about the H, Grey (a.k.a. Paul) if and when the mysteries are revealed?
I liked the story of the SC, Nerina and Mikhail, and their son, Grigori. That would have made one terrific novel, and I kind of wish the author had done that, as she could have added a lot more to everything that was revealed here. (This book makes you really consider what the word "freedom" means, how precious it is and how it should never be taken for granted, or abused, or turned into your own agenda.)
One thing I didn't care for all that much was the character of Steve, Grey's friend/colleague. While he did have to take their work seriously, I still don't think it was his call to decide if Kristin was ready to know the whole story, and the way he kept discouraging Grey from revealing the truth. Married couples shouldn't have secrets from each other, and Steve didn't seem to be concerned that Grey's being secretive could put a strain on his relationship with Kristin. Too many things weren't adding up and she was no dummy, she knew something was going on. Steve had reasons to be concerned, but he came off as being interfering and intrusive.
Aside from a few minor flaws, this was a really good book and worth your time.