This, the third in Duncan's alchemist series, is in my view the best plotted and succeeds best in including the arcane as a key thread as opposed to using it to avoid lengthy detection/interrogation. The author appears to have achieved a level of historical authenticity and acknowledges his sources nicely.
Except for one. Just as Conan Doyle's Holmes inspired a slew of clones, some excellent, some mediocre, and some just plain awful, so Rex Stout's Nero Wolfe has his follow-ons. Of which this is one. And a very, very good one at that. Need a genius-class detective who almost never leaves his digs but has a suave man-about-town to do his footwork? OK, Wolfe and Archie Goodwin. Or Nostradamus and Alfeo Zeno.
By the way, if you are interested in an excellent compilation of Holmes "parodies, pastiches, and ponderings", look up Marv Kaye's anthology "The Game is Afoot" (Truth in packaging note: Marv is an old friend of mine.)The Game Is Afoot: Parodies, Pastiches and Ponderings of Sherlock Holmes