Check the booklist. It has a solid list of history books addressing all eras of Chinese history.

What are you looking for specifically? A textbook? Biographies of key players? Historical fiction?

Diana Lary, Warlord Soldiers: Chinese Common Soldiers, 1911-37

This is probably going to be the closest to what you're looking for. It's about the life of soldiers through the Warlord Period. It's a rather short read, because the evidence is sparse.

Edward McCord, The Power of the Gun: The Emergence of Modern Chinese Warlordism

This book discusses the conflict at the provincial level, looking at developments in Hubei and Hunan after the collapse of the Qing empire.