The Viking Gods contains excerpts from Snorri Surluson's Edda, which was written around 1220 and is the most important source on the gods of the Vikings. The Edda has been described as "one of the best story-books of the Middle Ages." The Vikings believed that Odin and Thor and the rest of the gods were immortal, and history has proven them right. Their names are mentioned by millions of people every day, as the days of the week are named after the Viking gods: Tuesday after Tyr; Wednesday after Odin (or Woden); Thursday after Thor and Friday after Frey.