The Soul of Viktor Tronko by David Quammen (1987) - from the heart of the Cold War. American interrogators try to figure out if a Soviet defector with startling revelations is telling the truth.
Quammen has become well known as a writer on nature and the environment, but he started his career writing spy novels.
His earlier novel The Zolta Configuration (1983) is set in the atom bomb project during WWII. I recall Oppenheimer and his circle are characters.