There are a lot of questions we still have about the Vikings, mainly because they didn’t leave much in the way of contemporary written records. Gathered together, their runes don’t add up to all that much. Archaeologists can reconstruct a great deal of their physical culture — houses and ships and weapons — but their intellectual history is harder to track. This is, however, a subject Robert Ferguson doesn’t shy away from in this history, which reconstructs Viking history with an eye to its own (much later) historiography, focusing on the transformation of Viking religion from Heathen to Christian and the gradual absorption of Viking culture into the European legal and political mainstream. What continues to puzzle me is not what drove them but just how the Vikings were so successful in establishing their far-flung and long-lasting diaspora. That Europe was weak and divided and the Vikings unified and well-organized is one thing, but shouldn’t explain 300 years of such dominance. I still find it a mystery.