At her best, McDermid can enthral me with her crime fiction, but I find her work very uneven and, while diverting enough, this novel was not amongst the best of hers I've read.
Realism is never one of McDermid's core strengths, but when reading this novel, I didn't so much have to willingly suspend my disbelief as hang draw and quarter it. There's the usual problem that Tony's "incredible psychological insights" seem to amount to a couple of superficial deductions that a five-year-old could have drawn, a couple of findings that are down to plain detective work, not psychology, at all (e.g. the knot thing) and then some highly specific findings that come from nowhere. But, added to that, we have supposedly crack law enforcement teams and elite gangsters all behaving like the Keystone bleeding Kops, making basic schoolchild errors left, right and centre and exposing themselves to risk by insisting on performing menial tasks themselves that in RL would have been left to a minion at the bottom of the pile. And the whole premise of the covert operation which Carol is involved in starts off incredibly far-fetched and then breaks ever more stratospheric new heights of implausibility as the novel progresses.
The gangster theme in this book seemed to me to be, not only unconvincingly drawn, but pretty uninteresting.
One thing I dislike about McDermid is a tendency to include graphic acts of violence (and especially sexual violence) merely for titillating, sensationalist purposes. The second of the two brutal rapes in this book seemed to me especially unnecessary and included only to artificially prelong the dynamic between two characters well past its sell-by date.
On the plus side, though, the book was very readable - no mean feat, given that McDermid had, as always, included scenes from the murderer's perspective from the start, so had deliberately denied herself the easy route to suspense of a whodunnit. I also like the main characters and their relationship, although I think that has been better explored in other books of the series.