For the emperors from Hadrian to Heliogabalus (AD 117—222) our main source is an extraordinary literary curiosity, the Augustan History.
Written in the late fourth century by an anonymous author pretending to be a team of six much earlier biographers, it contains a solid core of historical fact but also makes lavish use of faked documents and includes many fictitious (but highly entertaining) anecdotes about the luxury and depravity of the emperors.
Suetonius's great masterpiece, The Twelve Caesars, covers the whole period from Julius Caesar to the death of Domitian in AD 96. In this fine modern translation of its only true sequel Anthony Birley has also bridged the gap by providing brief lives of Nerva (96—8) and Trajan (98-117). Together they provide a unique portrait gallery of the colourful and compelling personalities who ruled most of the known world during the greatest period of Roman history.