I, Claudius was on Ann Perry's list of favorites that I mentioned in a post on May 17. I just finished reading it. It is an historical novel written in the 1930s. Robert Graves, the author, drew together all sorts of historical materials concerning the reigns of Caesar Augustus, Tiberius Caesar, Caligula, and finally Claudius himself (him, briefly, but there is a sequel Graves wrote just about his reign). Graves used a fictional narrative purportedly written in the first person by Claudius.
I have been reading Livy's, The Early History of Rome, which is so densely written (at least to me) that I can only read it in short sittings - but I am making good progress. It is "history" and not fiction, but it has the same feel as I, Claudius without the characterizations that help move Graves' narrative along. I enjoyed I, Claudius, and I continue to enjoy the bits and pieces of Livy that I am reading. (I'll finish it one day.)
Maybe you saw the Masterpiece Theatre series, I Claudius. It was broadcast at a busy time of my life, and I didn't get to see it. But I've ordered the first two DVDs of it from NetFlix. It was allegedly the most popular Masterpiece Theatre series of all time.