The Hammer and the Cross (Hammer & the Cross, Book 1)

Blurb

The Hammer and the Cross is the first part in a trilogy written by Harry Harrison and John Holm, a pseudonym for the Tolkien scholar Tom Shippey. The book chronicles the rise of the protagonist Shef, bastard son of a Viking and an English lady. The book is set in the 9th century England where Viking raids are common and presents an alternate history to the one we know.
Within this tale, the authors explore what might have happened if the Vikings had waged more of a fight against the rather harsh, at that point in time, rule of the Catholic Church. Central to this story is the protagonist Shef. In the story an ambivalence concerning Shef's birth is introduced: Is Shef the son of the Norse god Ríg, or a Viking named Sigvarth? And are the gods real or just dreams? These ambiguities develop through the trilogy.