If one aspect of this book were different, it would have been a 5-star read for me. That aspect is the existence of Aidan. It was almost comical how useless he was. He spent the entire book being incapacitated in one form or another. He hindered Bryn every step of the way. Also, why did they even have a relationship? They hated each other, shared two sentences, kissed, and then were in love? Like, actually saying they loved each other. At first, I hoped Aidan would turn out to be a villain and that he was just using her. Then, their nonsensical relationship would actually start to make sense. But, that wasn't the case, and I was seriously just sitting there, wondering how I was supposed to believe in their "love."
Aside from Aidan, I really liked this book. It sucks that he was a main character. Some of the other characters were a little too "over-acted," such as Freya and sidekick-Valkyrie-what's-her-face. They weren't too annoying though. I loved Fenrir and wished he had been the one to go on the little mission with Bryn. He is a much more tolerable character than Aidan. I also really liked Loki. He was written very true to mythology.
Some people complain that there was too much world-building and "filler," but those parts in Asgard were some of my favorite in the book. I really liked experiencing Asgard through Bryn's eyes; it was never boring to me.
One thing I found a little ridiculous and unbelievable was the fact that they only retrieve a few new warriors per week or so? Ok, cool, apparently the warrior heart is a rare thing on Earth. Understandable! Oh, but wait... Four of them came from the same city. Apparently, it's not that rare of a thing. With that in mind, there should be thousands of Valkyries and thousands of warriors brought back every week. What about other parts of the world, too? It just wasn't very realistic and was something of a Santa complex (too many people, too little time).
Overall, I liked this book, but I'm pretty sure Aidan and their "romance" is going to keep me from reading farther into this series.