Every brilliant eye - Loren D Estleman

To hear him tell it, Amos Walker is an unsuccessful man in an obsolete profession. Still, even P.I's have a sense of honour, and Walker has always been a man who believes in paying back favours that people have done for him over the years. He owes his old friend Barry Stackpole a big one, for saving his life in a Cambodian shell crater a lifetime ago.
Now Stackpole, lately a good, hard-scrounging reporter, has vanished. And finding him is the job Walker's been hired for - not once, but twice: first by Stackpole's newspaper, then by an attractive literary editor hot to track down an even hotter book the missing man's been writing.
The investigatory trail becomes littered with a bewildering assortment of fresh dead bodies. Walker nearly joins the clutter when somebody rigs his steering and brakes. And a final revelation explosively narrows the distance between the tropical jungles of Asia and the concrete jungles of Detroit, and between one brand of war and another...