1. Know going in that the book is about Augustus, Tiberius, and Caligula, and not really about Claudius as Emperor.
2. If you want to know more about Roman history, this is a great book. He personalizes all these figures into the "horny Stalin" types they really were. I feel like I know how the whole Imperial Rome thing worked now, and why Caligula was a bad guy (or at least, the few remaining historical sources make him out to be such a bad guy.)
3. As a "novel," it's a bit of a slog as you get very few scenes where Claudius talks to people. He's mostly talking about other people's lives and historical events.