If you liked...
If you're a fan of Deanna Raybourn's Veronica Speedwell Mysteries, I have a sneaky feeling you'll enjoy A Study in Scarlet Women, the first the Lady Sherlock series. These two books have some of my favorite things in common: Regency era historical fiction, a mystery with an ending I couldn't predict, and a rebel protagonist in a time when women were meant to be demure. (And if you haven't yet been introduced to Veronica Speedwell, then might I suggest putting both of these books on your list.) In my review of A Curious Beginning, I loved Veronica for her audacity, brilliance, and spunk. I loved Charlotte, our Lady Sherlock, for the same reasons. In A Study in Scarlet Women, Charlotte is forced to leave home after a scandal. In need of a new position and a new path in life, she becomes Sherlock Holmes, mysterious consultant to those with a mystery in need of solving. Sherry Thomas did an excellent job with her creative use of the canon, and I came away with a great fondness for the cast of characters in this book. Also recommended for those who enjoyed Duels & Deception (another great historical fiction in this era with a strong female lead).
P.S. I'm already looking forward to reading the next in the series, due out in September. You can see a review of it right here on TST soon, but in case you're impatient (like myself), you can pre-order it here.