Kang's best-known and probably most controversial work is "Da Tong shu" (大同書). The title of the book derives from the name of a utopian society imagined by Confucius, but it literally means "The Book of Great Unity". The ideas of this book appeared in his lecture notes from 1884. Encouraged by his students, he worked on this book for the next two decades, but it was not until his exile in India that he finished the first draft. The first two chapters of the book were published in Japan in the 1900s, but the book was not published in its entirety until 1935, about seven years after his death.