I loved this book. It takes place in a "skewed Regency", a.k.a. "hard-boiled Regency", inspired by both Jane Austen and Dashiell Hammett. The very beginning is a takeoff of Austen:
"It is a truth universally acknowledged that a Fallen Woman of good family must, sooner or later, descend to whoredom."
Our heroine, Miss Sarah Tolerance (nee Brereton), is a 28-year-old Fallen Woman. After eloping with her brother's fencing instructor at 16, they went to Amsterdam and had a fencing school. After he got sick and died, she returned to England and became an "agent of inquiry" (i.e. private investigator).
"Miss Tolerance had believed her new-wrought profession would make her independent and spare her the choice of death or whoredom. Apparently it was not to be so simple."
Miss Tolerance is hired to locate a missing Italian fan, given to a now-retired whore from her former lover. The former lover's son, the Earl of Versellion, has been warned to get it back, but he has no idea why. Whatever the reason is, it seems to be quite deadly, as people start dying, Miss Tolerance has to fight people off with swordplay, and attempts are made on her employer's life.
Okay, so I'm partial to liking anything compared to Buffy on its cover, even if this is no fantasy, but Miss Tolerance is a smart girl who kicks booty and manages to outwit people, figure things out, and do the right thing regardless of the cost. I need to find the other book about her by the author now...