The Merman's Children

In the waning years of the Middle Ages, before Christendom had completely scoured the world of magic, both Faery and Man lived on Europe's shores. This is the story of those last days: of the halfling children of the Liri king, who were of both realms but chose the one we call the other; of how they schemed and fought for survival, hounded from the Baltic to the ice caves of Greenland to the Mediterranean coast; of how they loved and how they died.
It is the epic master piece, the adventure at once erotic, violent and magnificently sad, that Poul Anderson has always wanted to write.