Dean Koontz's Mr. Murder

What is Dean Koontz's Mr. Murder about (plot, summary)
Marty Stillwater, a mystery novel writer, discovers he has a clone. Although they share the same physical appearance his double has the personality of a murderer.
Marty Stillwater, a mystery novel writer, discovers he has a clone. Although they share the same physical appearance his double has the personality of a murderer.