Gibbon, Edward, and David Womersley, The History of the Decline and Fall of the Roman Empire, abridged ed., Penguin, 2001.

First completed in 1788, Gibbon's classic study of the Roman empire continues to be considered one of the major works on the subject. Womersley's abridgement keeps the major themes and style of the original.

Graves, Richard Percival, Robert Graves: The Years with Laura, 1926—1940, Viking, 1990.

The second of a three-volume biography of Graves by his nephew, The Years with Laura covers the period in which I, Claudius was written.

Graves, Robert, Claudius the God: And His Wife Messalina, 1940, reprint, Vintage, 1989.

Picking up where I, Claudius left off, Claudius the God: And His Wife Messalina covers the 13-year reign of Claudius as emperor of Rome.

Seymour, Miranda, Robert Graves: Life on the Edge, Doubleday, 1995.

One of the most insightful biographies of Graves available, Seymour's work profited from the...