This narrative, which leans heavily upon the usual suspects (Suetonius, Pliny and Tacitus) is a conversational textbook - a popular version of a book of learning, much like I, Claudius - very much in vogue throughout the latter half of last century. It delivers a potted biography of Julius Caesar and his eleven direct replacements - from Augustus to Domitian.
As a work, it delivers simply what it suggests on the packet: small bios, pieced together from influential - but hardly neutral - sources. Grant time and again points out that Suetonius tended to highlight the sexual depravities of his subjects, while Tactitus' words showed contempt for each of the three Caesars who rose to their position via civil war (Galba, Otho and Vitellius).
He delivers simple, effective portraits of highly complex men - figures simplified by period literature through rumour and suggestions being made out as fact. He is even-handed and resists editorialising, except for during the last chapter where he tries unsuccessfully to "sum up" and only manages to confuse himself and his readers.
Unfortunately, there really is very little else to say. Grant writes as an academic, with economy of emotion, as if just putting words down on paper for future generations. If you're interested in the period or a history buff, then it's certainly worth a look - otherwise the source material may prove a little dry. Tennis balls.