This is an excellent read which takes us back to the romance, excitements and pleasures of Regency society. The writer is obviously thoroughly at home in the period's history and morality and acutely aware of the repressions that contemporary women had to suffer. Her central character, Lydia, shares that awareness and, while remaining polite, circumspect and fully conscious of the role expected of her, shows a refreshing and entertaining independence. Even as we see her holding her tongue and tolerating the insinuations and attentions of the men around her, we know she's at least their equal.
And the interactions between all the characters are minutely observed by the writer. Their dialogue has real authenticity, they're all drawn with wit and economy and there's a constant awareness of body language and surreptitious glances which reveals exchanges other than those being spoken. In fact, there's so much more going on than the surface reveals (hence the title). The episode where Lord Sheldon rubs salve into a bruise on Lydia's shoulder is understated, discreet, and very sexy.
In the background and, indeed, influencing the development of the plot, is the figure of Bonaparte and the activities of French and English spies, all of which adds to a tale which captures and transmits the ethos of the period. And there's even a guest appearance by Lord Byron. Regency romance at its best.