This is an entertaining book about the life of Nell Gwyn, favorite mistress of Charles II of England. It moves briskly, covering 8 years of her life and introducing a large number of characters from the royal court. I enjoyed this book and would recommend it as a good light read, with the added bonus of learning some British history; however, nothing about it really stood out. The epistolary format works well in some ways: by including a variety of diary entries, letters, gossip columns, official papers and so on, the author keeps things moving and is able to give a sense of the wider picture. This also allows the book to cover eight years without awkward time-skips. On the other hand, the modern language is jarring when it's purported to be the characters' own 17th-century writings, and nobody really writes a diary the way Nell writes hers here (complete with dialogue, entire scenes and so on).
Also, while the characters have some personality, the epistolary format seemed to get in the way of knowing what they were really like as people. I would have liked to see Nell from a third-person narrator's point-of-view; she seemed like a great character but didn't quite reach her full potential. I was a little disappointed that the author chose to take out some of the spicier parts of her character; for instance, where she's reputed to have given a romantic rival a laxative, the book portrays her as innocent, and it eliminates sassy remarks she's reputed to have made (for instance, when her coachman nearly got into a fight to defend her honor, she's reputed to have said, "I am a whore. Find something else to fight about"). She's still sassy and fun here, just a bit whitewashed.
A couple of notable secondary characters: Aphra Behn is great, and I've love to read a book about her (so she was a spy, and traveled the world, and was one of the first professional female writers.... remind me again, why are we reading about Nell Gwyn instead?). Teddy seems to get a lot of love, but he's such a stereotypical gay character, of the woman's-BFF-in-romantic-comedy variety. I quite liked reading about Nell's family, though, and thought her previous affairs were well-handled.
At any rate, this novel is decent fun and would make a great beach or airplane read. Nothing really memorable, but nothing seriously wrong either.