The story focuses on the shenanigans surrounding one Lady Susan Vernon: a scandalously flirtatious recent widow who spends her time conniving men (married and single) into thinking her a good woman and mother (of which she is neither). She is older, beautiful, witty, and charming. The women see through her lies and deceits and flattery, while the men in her presence fall prey to it.
It's an interesting set up. As a female character in that time period she must be despised for her immoral nature, but yet she is a very commanding persona that triumphs over typically-considered-stronger males. She is both the namesake and the "villain" of the story--she truthfully has no redeeming qualities. But Lady Susan is not the one strong female, however, since the other women see through her character. It is a novel where female characters are more intelligent and sensible than males. For me, it's the dominance of female characters that is most interesting, particularly for the period. Or perhaps it's just an apparent dominance; are there men who, upon closer examination, are better characters?
While I don't dislike the epistolary format, for this novel I find it hard to get a true sense of the character I want to know best: Frederica, her daughter. I also don't like that I cannot see the moments of Lady Susan's seduction (however, I enjoy her recounts in letters to her dear friend).
The tale is dark for Austen--terrible parenting and a somewhat rushed conclusion to the work. It's a very different read than any of her other works I have encountered. Yet it shows her range and it does not feel out of place within her works.
As a final note, if I had my way: Kim Cattrall would be playing Lady Susan in some adaptation of the book. She's divinely perfect for the role. Jane Seymour would be a far second.