Surprisingly, this book is not for the faint-hearted. Why was that surprising? Because of the tone of the writing.
Carr's style is erudite, to a fault. This novel reads like an academic tome, in parts. There are sections of the book that were truly frustrating simply because something exciting had just happened. A mystery is being revealed! A horse-and-buggy chase has ensued! A discovery has been made! But Carr places pages and pages of text, usually describing the milieu of a particular part of NYC down to the very last detail, in between the initial surprise and the reveal. Sure, that builds suspense. It also means I only skim those sections because I don't care all that much about the color of that brick building, especially when I just want to know who the next murder victim is.
This book also feels a bit contrived to me. Creating a female detective is all fine and good, but don't contrive to put her in particular situations or describe how she might feel versus how the men are feeling, at certain critical junctures. Sure, it's difficult to write a book set in the past, and also place it within the zeitgeist of the current times. But, combined with Carr's specific tone, this didn't sit at all well with me.
And the reason it's not for the faint-hearted? Because of the author's developed tone and his plotting, you would expect not as much violence, not as much blood, not as much horror. It's pretty much all of those, people, so be forewarned.