Bombs Away

Bombs Away by Harry Turtledove
432 Pages
 
"China decides it cannot risk the possibility of America's total victory in the Korean War, and, just five years after Japan's surrender to the U.S., the People's Republic of China joins the Democratic People's Republic of North Korea in the war to preserve and spread communism throughout the Korean peninsula. In response, a frightened U.S. annihilates Manchuria with its most effective weapon to date: the atomic bomb.This leads to retaliation by the Russians and the slide into World War III."

Turtledove is known for his alternate history book and this one explores the premise of Truman allowing MacArthur to utilize the atomic bomb in the Korean conflict.  The weakness of the book is that there is little character development so you don't get very invested in their fates.  The escalation of hostilities between the US and Russia wears on the reader and the horror of the war is numbing.