The Devil in Music
Historical mysteries are tricky. Some authors seem to believe that their primary goal is to impress the reader with how much they know about the period. Others use characters who are obviously modern people with modern attitudes in period drag. A non-trivial number simply don't know how to write a mystery plot.
Kate Ross did it better than most. Her period is the 1820s, and her characters are of their time (her detective. Julian Kestrel, is an English dandy in the mode of Beau Brummel). She's got a deft hand with period detail; instead of inserting a factoid every few paragraphs, or smothering the reader under periodic infodumps, she works it seamlessly into the narrative. The Devil in Music is a historical mystery that actually feels historical.
It does not, perhaps, feel quite so mysterious. The central twist in the murder plot is taken from a classic Dorothy Sayers novel. There's also a more intrigue-oriented side to the plot, and that's more satisfying. Without spoiling anything, there's one very clever and completely appropriate piece of misdirection that deserves some kudos. Finally, the resolution involves some pretty good character development.
So: The Devil in Music didn't make my jaw drop, but I quite enjoyed reading it. We already own the first book in the series, Cut to the Quick; now I want to read the others.
If you could somehow combine Kate Ross with Susan Spann, you'd get something spectacular. Spann doesn't have Ross's writing chops, but she's a better technician.