This is not a novel for everyone. In some ways, I think that should be preface of every Mitch Cullin novel. Because though he writes with a stark and beautiful prose, he often addresses subject matter which deals with the fringes of human existence. Under Surface is no different. This is a haunting portrait of the shadowy side of human sexuality, and the base desire that drives one to do something he wouldn't ordinarily do...and then to repeat it over and over until the thrill wears off and something deeper must emerge to take it's place.
At it's most basic level, Under Surface is a cautionary tale dealing with the dangers of suppressed desire finding secretive outlets. After growing less and less cautious about his illicit rendezvous, the man character finds him in the wrong place at the wrong time and consequently loses everything. But it's Cullin's gift for storytelling that makes this story compelling, by allowing the mystery unravel in bits and pieces.
On another level, this book is a challenge to morality, and what we consider right and wrong and the way those conventions push individuals into unsafe choices. But also is about how those moral complexities create and breed darker desires within us, and how those desires can make us lose sight of what we truly value.
As I said, this book may not be for everyone, but it probably should. We all have demons we must face through life. This is the kind of book that forces you to examine your own.