Vie des douze Césars
He is mainly remembered as the author of "De Vita Caesarum"—translated as "The Life of the Caesars" although a more common English title is "The Lives of the Twelve Caesars" or simply "The Twelve Caesars"—his only extant work except for the brief biographies and other fragments noted below. "The Twelve Caesars", probably written in Hadrian's time, is a collective biography of the Roman Empire's first leaders, Julius Caesar (the first few chapters are missing), Augustus, Tiberius, Caligula, Claudius, Nero, Galba, Otho, Vitellius, Vespasian, Titus and Domitian. The book was dedicated to his friend Gaius Septicius Clarus, a prefect of the Praetorian Guard in 119. The work tells the tale of each Caesar's life according to a set formula: the descriptions of appearance, omens, family history, quotes, and then a history are given in a consistent order for each Caesar. He recorded the earliest accounts of Julius Caesar's epileptic seizures.