Ruin Value: A Mystery of the Third Reich - J. Sydney Jones

In 1945 Nuremberg, an American intelligence officer tracks a killer: "Powerful . . . Fans of WWII mystery fiction should consider this one mandatory reading" (Booklist).
Nuremberg is a dead city. In the aftermath of World War II, two-thirds of its population has fled or is deceased, with thirty thousand bodies turning the ruined industrial center into a massive open grave. Here, the vilest war criminals in history will be tried. But in Nuremberg's dark streets and back alleys, chaos rules.
Captain Nathan Morgan is one of those charged with bringing order to the home of the war crime trials. A New York homicide detective who spent the war in Army intelligence, he was born to be a spy—and now, in 1945, there is no finer place for his trade than Nuremberg. As the US grapples with the Soviets for postwar supremacy, a serial murderer targets the occupying forces. Nathan Morgan may be the perfect spy, but it's time for him to turn cop once more.