This is the cover of the paperback edition of the book. The hardcover looks essentially the same, save for the inside flaps on the dust jacket.

The backgrounds are photographs. The character on the front was created with a 3D figure modelling software package called Poser. She is one of several characters in the novel, which features an ensemble of characters who are all more than they initially appear. But the scene depicted actually does not occur in the story. There's a beach (it's an island, right?) and a knife, but that character never stands on the beach with the knife behind her back.

So why make that my cover illustration? I guess it's because when the image popped into my head, I found it a striking one. More significantly, it accurately represents the spirit of the story. A knife behind one's back is a most deadly secret, a hidden darkness that may reveal itself in a burst of violence at any moment. The image is fitting.