Is the "hail Odin" quote a real thing in modern prisons or was that you add in? I really enjoyed to book, but wondered where this fit?
Yes, it is a real thing. Odinism is a popular religion among white inmates in many prisons. In some prisons inmates have created formal groups that practice Odinism, which they see as a celebration of the Norse faith. I've worked with a fair number of white inmates who say they are an Odinist. They do greet each other with "Hail Odin."