Red Wings over the Yalu: China, the Soviet Union, and the Air War in Korea by Xiaoming Zhang. This is a great addition to the history of the airwar in the Korean war. Based on research on previously unavailble sources in China and Russia, Zhang have created a very interesting history from the Chinese side.

Odd Man Out: Truman, Stalin, Mao, and the Origins of the Korean War.  The book presents a list of arguments to turn the conventional wisdom regarding the role of USSR, China, and United States in the Korean War.

Convetional wisdom: US was totally surprised by the invasion, the war was started by Kim despite the misgivings of both USSR and China. Thorton thinks otherwise.