"It is a truth universally acknowledged that a Fallen Woman of good family must, soon or late, descend to whoredom."
from this 1st sentence in Point of Honour by Madeleine E. Robins, i was totally hooked. (doesn't this already sound like a 4th grade book report?) This book blends some romantic elements with mystery, intrigue, and an alternate universe of Regency England all in one. Even sticklers for historical accuracy will enjoy the deviance of a reigning Regent Queen! I wish there were more fencing master female "agents of inquiry" who live behind their aunt's upscale whorehouse in reality, but until then, I am happy to sink into the ether of the tales of Miss Sarah Tolerance, fallen woman-turned-investigator of the sordid underbelly of the Regency upperclass.
If any of this makes any sense (it is 2 am after all) you will rush out to your nearest library and obtain this first book of the series. (There's only 2 right now. The second book, Petty Treason, is really good too. Read them in order unless you want to ruin everything!)