First of all, I should state that I haven't previously read any of QJ's other books. I would not recommend this to anyone else who hasn't done so. There is a huge list of characters who aren't really introduced to us, because we're expected to have read the other books first. It also helps if the reader has some understanding of the command structure of the police force (fortunately I did) otherwise we have no idea who is whose boss or vice versa.
The first two-fifths is pretty boring. Not much happens, there's a lot of talking, a lot of interaction between characters who the first-time QJ reader knows nothing about.
The second two-fifths is much more interesting as the body count begins to rise, and they start rounding up the suspects. However, I felt that the investigating police officers didn't behave very realistically or professionally - they seemed to let personal feelings govern the way they treated their suspects. As I work for the police force, this stuck out like a sore thumb.
The last fifth goes down like a lead balloon. When the killer is finally revealed, my only reaction was bewilderment. The motive given was completely underwhelming and constituted little more than a couple of sentences of explanatory text. I'd worked out who it was but couldn't imagine why he/she would do it, or why he/she would be trying to frame Bob Skinner.
On a humorous note, the book lost all credibility when it suggested that Hibernian FC had won the league...