I'll give it 3.5 stars. 
 I enjoyed the Icelandic mythology. I liked the characters, and compared to some of the YA I've read lately, it actually has an ending, which is a good thing. Things went so fast, which is both good and not so good. Good because I was easily drawn into the story. Not so good because some things were solved a little too quickly. Not sure if this is meant as a series or not. There are certainly plenty of threads left hanging.