Whilst I found this book fascinating, I also found it frustrating. There is no fresh insight into any of the already fairly well documented cases that McGregor focuses on, which is disappointing. There are attempts to titillate and stimulate readers' imaginations in the narrative style the author adopts, but there is little to get one's teeth into (which given the evidence in some of the cases may be rather crass phrasing!). I had expected at least detailed accounts and also possibly a few fresh insights or discoveries, especially in the instances of unsolved cases.
The one or two instances where descriptors such as "perverted" or "depraved" or "brutal" we're used, there was little by way of explanation, leaving the reader wondering what on earth the author is referring to? I'm not suggesting that graphic detail should be included but something along the lines of background/evidence/ history to clarify rather ambiguous labels.
Of course this book is 7 years old now and may well have been superseded by others. It's a decent read but offers nothing extra to what can be gleaned from thorough google searches.