I, Claudius by Robert Graves.
It spans from the reign of Emperor Augustus to the death of Emperor Claudius, Augustus' grandson. It illustrates the corruption and power struggles in Rome's royal family. It is only semi-fictitious, everything that can be known about the time and the people involved is accurate, Graves just used artistic license to put it all together into a story.
It was made into a BBC television series in 1976 which is, believe it or not, excellent. I just checked and it has an IMDB rating of 8.9/10, I own it and have watched it through atleast 3 times.
Stars include a young Jean-Luc Picard(Patrick Stewart

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