Poul Anderson 
War of the Gods 

The story of the great King Hadding is one of the darkest and most violent to come down to us from the old North. Hadding was raised by giants far from his rightful throne, as his father, a Danish king, was slain shortly after Hadding’s birth. But the time comes when Hadding feels he must reclaim his legitimate place in the land of the old North. He must endure ferocious battles, the charms of voluptuous Valkieries, and a War of the Gods to rival Armageddon.