I came across this book as a result of reading the much more recent "The Invention of Murder" by Judith Flanders.
This is an old book,originally published some decades ago, but noetheless readable or interesting for that. As a friend of mind said (after reading it on my recommendation) "the combination of a criminologist and a fiction writer works really well".
PD James is, of course, well known as a long-standing and eminent writer of detective fiction.
The case involves two sets of very bloody murders in a very short period of time and close proximity. The search for the murderer, the suspect's fate and the possible alternative candidate as killer provide the narrative backbone of the book.
So far as this "true-crime" valume is concerned, the period, the location and the characters (and what an incredible crowd they are) come alive. The tragedy of these awful crimes - and they were tragic on several levels - is well brought out. The only oddity (for me - and the reason this has been given 4 rather than 5 stars) is that the authors' solution seems very brief and almost "tacked on". I would like to have seen this explanation gone into in a little more depth. But that does not detract from the book as a whole.
For those who have not already discovered this book, I recommend it, whether you like a mystery, are into the social history of London or the Georgian period, or just want to enjoy a darned good read