Any book with a title like this is not aimed primarily at Oxford graduates, yet time and again, Cawthorne pretentiously uses Latin and doesn't bother to translate. Like Nigel Cawthorne's web site, this practice is all about trying to show how clever he is. If it was just common phrases, he might be forgiven, but when Cawthorne is quoting obscure Roman commentators, the average reader has no chance of understanding or inferring the meaning.
That one major criticism aside, the book is not too bad. Unlike Stephen Barber's salacious, and monstrously inaccurate work Caligula: Divine Carnage, in which Barber goes on what appear to be deviant sexual journeys of personal fantasy, one does not get the feeling with Sex Lives, that Cawthorne had his pen in one hand and his penis in the other. It's moderately restrained, and almost seems schizophrenic, mostly talking in scholarly but usually unpretentious language about the historical facts, but then occasionally slipping into schoolyard expressions like "shagging" and "nookie".
It very much depends what you are looking for. I bought Barber's book because I was interested in all the sordid details, but it was so clearly written to arouse the degenerate mind, that it was almost unreadable. Sex Lives has been titled to tittilate, but written to educate, and I actually find it a more interesting insight into the Roman culture. Both books spend much time talking about the pedaristic homosexual practices of most emperors, but whereas Barber almost writes with a tone of longing, like a person who was not invited to a really popular party, Cawthorne writes with a kind of non-judgemental, neutral detatchment that enables you to see a wider scope.
I particularly like the way that he quotes multiple commentators and observers from the times, as well as works by the emperors themselves. Unlike Barber, he keeps ridiculous and lewd conjecture to a minimum, theorising only around what the facts suggest, and making it clear when he is doing so.
The problem with this subject matter, is that if Cawthorne got too close to the practices of the emperors, it would almost have transformed the reader from interested observer, to aroused voyeur (which is perhaps what the book's title implies it will deliver). As a result, he sometimes runs short on detail, and pads the book with wider Roman history and politics. This does still have relevance to the relationships the emperors had, but it leaves one wanting to know more either about precisely what the emperors did, or about the other characters, many of whom were more interesting.
Overall, this is a fair read that (sometimes too carefully) walks the line between crudeness and political correctness.