John Everson's Siren is $0.99 at Amazon. I haven't read it yet, but I do have the old leisure paperback (and now the ebook).
Night after night, Evan walked along the desolate beach, grieving over the loss of his son, drowned in an accident more than a year before. Then one night he was drawn to the luminous sound of a beautiful, naked woman singing near the shore in the moonlight. He watched mesmerized as the mysterious woman disappeared into the sea. Driven by desire and temptation, Evan returned to the spot every night until he found her again.
Now he has begun a bizarre, otherworldly affair. A deadly affair. For Evan will soon realize that his seductive lover is a being far more evil...and more terrifying...than he ever imagined. He will learn the danger of falling into the clutches of the... SIREN.