Short(ish), modern, London-based crime novel one of the short series of 'Factory' novels. The 'Factory' being the police department dedicated to low-profile murders.
This is psychological rather than action driven told from inside the heads of the psychopath, the unnamed police sergeant and the writings of the slaughtered Dora.
The policeman has to face up to the daily horrors of his job whilst society purports to care but doesn't want to face up to the evil consequences. He is challenged to the limit about the ends justifying the means.
This is a provocative novel about crime, rather than a crime thriller. It is designed to shock. Be WARNED - this is grim and violent to the level of an 18+ rating. For me, it succeeded in shocking but, overall, I felt it just didn't merit the semi-cult status it seems to enjoy.