The year of the locust : a thriller / Terry Hayes.

Enhanced descriptions from Syndetics:

In this "absolutely brilliant, tension-filled tour de force" (Brad Thor) from New York Times bestselling author Terry Hayes, CIA spy Kane confronts an evil that could bring the world to a cataclysmic end .

If, like Kane, you're a Denied Access Area spy for the CIA, then boundaries have no meaning. Your function is to go in, do whatever is required, and get out again--by whatever means necessary. You know when to run, when to hide--and when to shoot.

But some places don't play by the rules. Some places are too dangerous, even for a man of Kane's experience. The badlands where the borders of Pakistan, Iran, and Afghanistan meet are such a place--a place where violence is the only way to survive.

Kane travels there to exfiltrate a man with vital information for the safety of the West--but instead he meets an adversary who will take the world to the brink of extinction. A frightening, clever, vicious man with blood on his hands and vengeance in his heart.