Konnici na Liriite - Chevalier Du Lys

It is the tenth century, the Viking era is waning and Christianity beginning to supersede the old Norse beliefs. Hakon is a young boy brought up on the Norwegian coast, and, having survived being struck by lightning, he is chosen to be the priest of the old religion and keeper of its secrets. But Hakon's calling is not an easy one - there are jealousies at home, and during a raid on his village he is seized and enslaved. His journey takes him to the Byzantine imperial court, where he spends years as a member of the Varangian guard, the Emperor's elite bodyguards. Gaining his freedom, Hakon eventually returns to Norway to resume his position there. Again, stability is short-lived: this time his existence is threatened by missionaries of the new religion, and he sets out on another, even more dangerous mission that takes him further than he could have imagined, in an attempt to preserve the ancient life and beliefs of his people.
Several errors that made me not enjoy the book as it should...
First the Germanic beliefs were polytheistic (many gods), not pantheistic as Watkins describes (i.e., that they saw godhead or lifeforce in everything). His depiction of the origin of the Nordic pre-conversion belief is simply preposterous.
Thunder God is an average story with shallow characters and short on detail. I found it lacks the grit and realism of Household Gods and the historical accuracy of Severin's Viking trilogy- books that have in abundance what this book tried for.
Other Mistakes... Kari it's a man's name... (see Njal's Saga for the exploits of Kari Salmondarsson, one of the great viking heroes of all time).
In one remarkable oddity King Olaf Tryggvesson is repeatedly referred to as Trygvesson or King Trygvesson as though this were his last name. In fact, it wasn't since last names were not used in those days. Hakon Magnusson's own name poses a problem, too, since the name "Magnus" is Latin based and entered the Norse lexicon with the coming of the Christian priests. But the era in which Hakon's father grew up is clearly pre-Christian so his name is remarkably out of place.
It's just unrealistic to suggest that dragon ships were easily manageable by one or two or even three men alone as Watkins does. While he does seem to have familiarity with sailing, he doesn't convincingly translate that into a description of how Norse sailing vessels actually worked.
The dialogue and mindsets of the characters also ring false. Olaf tells the returned Hakon that their old childhood friend Ingolf "hates (his mother) for never letting him grow up as much as he hates himself for never having the courage to move out on his own." (p. 115)
There are other passages that seem unrealistic and out of time...
In the end, this is readable and, if you aren't too hung up on historical accuracy, characters appropriate to their era, and stories that are tightly plotted, you may want to give it a try.