A Wilderness of Glass by Grace Draven

The treacherous waters of the Gray have widowed many women in the village of Ancilar. But the sea gives back as well as takes away, something Brida Gazi discovers one bleak autumn morning while harvesting sea wrack on its storm-battered shore.

Wounded and stranded ashore, the merman Ahtin lies dying among the tidal pools until a land-walker woman, who can call forth magic with a mysterious flute, rescues him. Ahtin finds himself unable to resist Brida’s allure – or her magic – despite the risk to himself and his people.

But Ahtin isn’t alone in his fascination. Another, driven by bitterness and relentless purpose, seeks Brida and her unusual talent to manipulate for his own schemes, and neither Ahtin’s devotion nor the sea’s ancient sorcery will stop him from realizing those ambitions.