The Twelve Caesars is a set of twelve biographies of Julius Caesar and the first 11 emperors of the Roman Empire. The work was written in 121 during the reign of the emperor Hadrian, while Suetonius was Hadrian's personal secretary. On the Life of the Caesars concentrates on the acts and personalities of the Julio-Claudians and their immediate successors. Together with Tacitus' Annals, this work is a major source for the historical details in Robert Graves' novels "I Claudius" and "Claudius the God". (Summary adapted from Wikipedia by Karen Merline.)