Recommendations?

So today I was flipping through the channels and just happened to stop on the History Channel and watch some episodes of season 2 of Vikings. I haven't watched it before now and was absolutely fascinated by it so I'm planning on watching season 1. Until I get to that I was wondering if anyone knows of any good historical fiction books about Vikings, interesting non-fiction books about the Viking Age, or books (fiction or nonfiction) about Norse mythology.