His most famous work has become more accessible since it has been translated by Robert Graves, who must have relied heavily on it for his novel I, Claudius.  
Einhard wrote The Life of Charlemagne in imitation of this man's writings and he is the main source for the life of the comedian Terence which, along with a life of Horace, are the only two fully extant sections out for his largest work, De Viris Illustribus (On Illustrious Men).  His most famous work has become more accessible since it has been translated by Robert Graves, who must have relied heavily on it for his novel I, Claudius.  FTP name this 2nd century Roman author who wrote biographies of the first twelve emperors from Caesar to Domitian.
Einhard wrote The Life of Charlemagne in imitation of this man's writings and he is the main source for the life of the comedian Terence which, along with a life of Horace, are the only two fully extant sections out for his largest work, De Viris Illustribus
Gaius Suetonius Tranquillus