The Vikings. A History
by Robert Ferguson. This was a pretty good book but a very detailed book. Probably better as a book to
read for specific information rather than cover-to-cover, but still a good book.
The book put the "Viking Age" into the perspective of the interactions with the Frankish Empire of Chalemagne and his son and grandsons. I'd not read anything like this as most books on the Vikings are from the perspective of the raids into the British Isles. There was a lot of that too. The book also put the Viking Age into the perspective of the Christianization of the Scandinavian peoples.
There were also some good profiles of guys like Eric Bloodaxe and Ivar the Boneless.