Two good places to start:

 

Westad, Odd Arne. 2003. Decisive encounters: the Chinese civil war, 1946-1950. Stanford University Press.

The Chinese Civil War was one of the key conflicts of the twentieth century. The Communist victory determined Chinese history for several generations, and defined international relations in East Asia during the Cold War and after. Despite its importance and scope - its battles were the largest military engagements since World War II - until now remarkably little has been known about the war, and even less about its effects on the societies that suffered through it. This major new history of the Chinese Civil War attempts to answer two central questions: Why was the war fought? What were the immediate and the lasting results of the Communists' victory? Though the book highlights military matters, it also shows how campaigns were mounted alongside profound changes in politics, society, and culture - changes that ultimately contributed as much to the character of today's China as did the major battles. By analyzing the war as an international conflict, the author explains why so much of the present legitimacy of the Beijing government derives from its successes during the late 1940s, and reveals how the antagonism between China and the United States was born.

 

Lary, Diana. 2015. China's Civil War: a Social History, 1945-1949. Cambridge.

China's Civil War is the first book of its kind to offer a social history in English of the Civil War in 1945-9 that brought the Chinese Communist Party to power. Integrating history and memory, it surveys a period of intense upheaval and chaos to show how the Communist Party and its armies succeeded in overthrowing the Nationalist government to bring political and social revolution to China. Drawing from a collection of biographies, memoirs, illustrations and oral histories, Diana Lary gives a voice to those who experienced the war first-hand, exemplifying the direct effects of warfare - the separations and divisions, the exiles and losses, and the social upheaval that resulted from the conflict. Lary explores the long-term impact on Chinese societies on the Mainland, Taiwan and Hong Kong, which have all diverged far from pre-war Chinese society.