According to Wikipedia, "Gaius Suetonius Tranquillus, commonly known as Suetonius (ca. 69/75 – after 130), was an equestrian and a historian during the Roman Empire. His most important surviving work is a set of biographies of twelve successive Roman rulers, from Julius Caesar until Domitian, entitled De Vita Caesarum. Other works by Suetonius concern the daily life of Rome, politics, oratory, and the lives of famous writers, including poets, historians, and grammarians. A few of these books have partially survived, but many are entirely lost."