This is marketed the same way as Heyer's romances but be warned: while it has her trademark sparkle, it's explicitly a more serious historical novel, and may disappoint you if you pick this up thinking of Venetia, Frederica or any of Heyer's other classic romances.
I wasn't; I think it's one of her best novels. I like the story's intersection with real-life events, and the explicit discussion of class themes is interesting, although somewhat limited.
Jenny is neither pretty nor clever, but her loyalty, sensitivity (which she tries to hide behind a gruff, matter-of-fact exterior) and staunch common sense make her a compelling heroine. It's sad to think that she's still a somewhat unusual heroine today.