I have to echo the LibraryThing reviewer who said that if this sequel to I, Claudius is less impressive than the first book, it's because it's narrower in scope. I, Claudius isn't just this faux autobiography, it gave a run through of the members of the Julio-Claudian dynasty prior to Claudius--Livia, Augustus and Germanicus made quite the impression in that first book, which ended with Claudius being raised to Emperor of Rome. The focus in this book is his short reign of little more than a decade. And while the first book allows us to think of Claudius as crafty and only pretending to be an idiot (at least if you've never read Graves' source, Suetonius' Twelve Caesars), that's a lot harder here where he comes across as so, so clueless, at least in his personal life.
That said, this book is still an engaging read, and among the richest, best written works of historical fiction I've ever read. I've read Graves felt he was slumming it in his Claudius books, but it certainly doesn't come through. The picture he paints of early Christianity and Roman-era Britain is particularly fascinating. I only regret it's so hard to find more of Graves historical fiction in print. I loved his King Jesus, a story of a historical Jesus--married to Mary Magdalene--and published in 1946. Way, way before that travesty of a novel, The Da Vinci Code. But he also wrote other novels about the ancient world, such as Count Belisarius and Hercules, My Shipmate and Homer's Daughter I'd love to read. The Claudius books are his most famous though, and definitely where to start.