Set in 1795 London against the backdrop of the disastrous English-backed Royalist invasion of Revolutionary France, Elizabeth Redfern's first novel, The Music of the Spheres (2001) is a dark, rich tale of international espionage, astronomical observation, and diabolical murder. All three of those themes combine to create a very creepy literary thriller, best not read immediately before bedtime (which was, naturally, when I read most of it).
None of Redfern's characters are very likable (in fact they are to a person rather the opposite), but that only adds to the murkiness of the book. The author has, though, captured the essence of her time period and setting very well, and she's written a book which is sure to hold its reader's attention (even if it's only to find out what horrible thing happens next). The ending may be apparent somewhat in advance (it was for me), but even having guessed what was coming I had no idea how Redfern was going to get us there.
If you enjoyed The Alienist, or Instance of the Fingerpost, or The Interpretation of Murder, I'd recommend this one as well.