The Devil's Cub, by Georgette Heyer
I've enjoyed many of the Heyers I've read. This one I bought because it's about two characters I liked in An Infamous Army. Except Vidal was decidedly less likeable here. He's rather an ass.
Miss Mary Challoner has a younger sister, who is much prettier than she. Said sister begins a flirtation with Dominic Alastair, Marquis Vidal, who, of course, has no intention of marrying her. Mary intercepts a note for her sister from Vidal, which instructs her to meet him. She goes in her sister's place and ends up in France.
Vidal thinks she's as easy as her sister, but Mary isn't. Naturally, they start out hating each other, but they get over it eventually. There are also cousins and friends involved, and lots of lying and half-truths.
Vidal's mother may be the best character in the book. Leonie is from France, and she finds English customs rather silly.
I mainly wanted to shake sense into both characters. The Georgian period (this is pre-Regency, because Mary and Vidal are grandparents in Infamous Army) had some seriously fucked-up norms, where men spanked their wives as though they were children, for example. I have trouble sympathizing with a hero who wants to turn a grown woman over his knee and spank her as punishment for being "uppity." I know, 200 years ago things were different, but it's still very UGH.
I'm not sure how to rate this book. If you love Heyer, you'll probably enjoy it. If not, you probably won't.