Sima Qian invented the form Chinese historical fiction has used ever since: history told as a series of lives, each a self-contained biography with speeches, private scenes and a judgement at the end, rather than as a single chronicle. The Three Kingdoms is built that way. It moves between figures, gives each an arc and a characteristic virtue or vice, and treats invented dialogue and reported thought as legitimate parts of a historical account, which is exactly what the Records had licensed. Its immediate source is Chen Shou's Records of the Three Kingdoms; the reason a novel could be made out of a history at all is Sima Qian's method.