Just as Robert Graves did in I, Claudius this story purports to be an autobigraphy as told by a roman emporer. While that worked well for Robert Graves, this effort is of a feebler nature. It felt episodic but without the dramatic highlights that the earlier series had.
While this does a workman-like job of presenting the historic facts there isn't a lot that makes us care very deeply for any of these characters. The novel does give one a sense of some of the events and issues of the day but it fails to be compelling.
I think that there's still room in the story for a better book with more character development and perhaps some dramatic invention to entertain us and leave us with a better image of Hadrian and Antinuous, just as Shakespeare's Julius Caesar left room for Showtimes ROME. I'm not suggesting that Shakespeare's tale was anything less than great, but a new fresh perspective can often add dramtaic details that the original didn't feature.