1. Suetonius “The Twelve Caesars” (De Vita Caesarum)
How reliable is Suetonius?

2. “The Twelve Caesars”
The work, written c. AD 121 during the reign of the emperor Hadrian, was the most popular work of Suetonius who wrote a very great deal.
He started writing the Lives of the Caesars when he was Hadrian's personal secretary.
Suetonius

3. Suetonius used the imperial archives to research eyewitness accounts, information, and other evidence to produce the book.
However, critics say the book is founded on gossip and citations of historians who had lived in the time of the early emperors, rather than on primary sources of that time.
The book can be described as racy and packed with gossip. It is dramatic and sometimes amusing. There are times when the author subjectively expresses his opinion and knowledge.

4. Though he was never a senator, Suetonius takes the side of the Senate in most conflicts with the princeps ,as well as accepting the senators' views of the emperor.
This results in bias, both conscious and unconscious.

5. Suetonius was sacked after he had written the first two lives (Julius Caesar and Augustus) and he lost access to the official archives shortly after beginning his work.
He was forced to rely on second-hand accounts when it came to later emperors (with the exception of Augustus' letters which had been gathered earlier) and does not quote the emperor.
Like many of his contemporaries, Suetonius took omens seriously and carefully includes reports of omens portending imperial births, accessions and deaths.

6. Despite this, it provides valuable information on the heritage, personal habits, physical appearance, lives and political careers of the first Roman Emperors from Julius Caesar to Domitian.