I nominate 'The Records of the Grand Historian' by Sima Qian. It covers the beginning of Chinese history, to the first Dynasty (united mainland) of Qin 秦 and parts of Han 汉. Though it was completed in 109 B.C, what it known for is its absolutely unopiniated recording of the Emperors, or other people and events that were worthy of recording. He has recorded both the good deeds and the bads. But what is amazing is the perspective it offers- if Sima Qian could not personally verify a historical fact (sometimes he even travelled to the place it happened to see if he could discover more information) he would omit or note that he could not verify it. If there were two equally as likely possibilities, he sometimes would include both, in seperate chapters, and leave interpretation up to the readers. Even if a man was emperor, he was not guaranteed notice, and one or two sentences sufficed as an entry. Likewise, if a man was not an emperor but was supremely influential, no matter his birth, he would have his name down. No historian had his insight and fairness in recording a dynasty's history, and I think his work is worthy of being the greatest (I need to read all the others though to make a fair judgement).