I enjoyed the book especially for the Dumas connections and rare book world. The plot is interesting and moves along well although I didn’t enjoy the denouement. “Too much exposition” as Little Sally would say where there was too much explaining to try to make the plot work. Irene Adler was an interesting character that also didn’t develop into anything interesting.
Besides for a little letdown at the end I did enjoy it and it gave me some links to chase down (which are helpfully in the wiki article).