Well, I like them, but you're right -- Darling is usually a bit gristly. This one apparently earned mixed reviews. Those who read every Darling work published bemoan the change in atmosphere and claim that he's turned the villain into a milquetoast sop. I did always find Darling's villains rather predictable, though; it was his colorful settings and the research that he did to ensure their historical accuracy that appealed to me.
In any case, the other half of the reviewers claim that he's done a nice change of pace with this one. Apparently it's more thriller than crime gore. I haven't read it myself yet, so I can't say for sure.
Would you be interested in reading it with me? (It might help to keep me off this knee while I'm supposed to be healing. And if you find my manipulation transparent, well, it's only because I'm an acutely bad liar.)