IAN Rankin and Michael Connelly live half a world apart and yet seem to be joined at the hip. They both convey an intense sense of place: Edinburgh for Rankin, Los Angeles for Connelly. They both observe the seamy side of life with streetwise cynicism blended with the clinical detachment of a forensic pathologist. Their characters haunt the “mean streets”, which ever since the late Raymond Chandler have been traditionally the milieu of the private eye – and the cop.

The series characters of both authors are police detectives but significantly Connelly’s Harry Bosch and Ian Rankin’s Inspector John Rebus are so alienated from police culture they behave more like private investigators. Connelly has recently retired Bosch (Lost Light) and in this novel his protagonist is a company executive who dangerously plunges into the mean streets on a quixotic quest. In A Question of Blood, however, Rankin sticks to the protagonist who has helped make him one of the planet’s most read mystery writers.

Even by his standards, John Rebus’s career prospects look bleak. A petty criminal, Fairstone, who had been sadistically stalking his friend and colleague, Siobhan Clarke, has been found burned to death. Arson is almost certain. Can it be a coincidence that a few days later Rebus emerges from hospital with his hands heavily bandaged? When it emerges that he was trailing the deceased on the night he was killed, Rebus’s superiors turn very hostile.

Complaints and Conduct Division would be rubbing their hands if only they could get in touch with Rebus but fortunately he and Siobhan (pronounced “shivawn”) have got themselves attached to the investigation of a shooting at a private school in Leith. Two schoolboys dead, one seriously wounded, and the killer appears to have then turned the gun on himself. The shooter was an ex-SAS soldier, Lee Herdman, and this has resonance for Rebus, who had failed to get through the sadistic training he experienced trying to join the SAS.

Herdman had successfully built a business at Leith docks based around a high-powered motor launch. Why had he gone to the school and opened fire in a senior boy’s common room? Was he a man unhinged by earlier experiences and thereby moved to murderous rage? (Is Rebus perhaps also a human time bomb as a result of his army experiences – and is the death of the unlamented Fairstone the result?)

Rebus and Siobhan go to a community that is shattered by the apparently random tragedy. But was it random? Above all, why did Herdman strike when and where he did? The families are desolate. The father of one boy turns out to be a cousin of Rebus. He had known him as a boy but had never met since. He too is showing strange obsessive behaviour in the throes of grief. Then there is an unlikely duo from the army’s Special Investigation Branch. What are they searching for? The high-powered speedboat may have been used for smuggling but it is not clear contraband was involved. Meanwhile Rebus keeps an eye from afar on the Fairstone case and distance does not impair his detective skills.

There are indeed many interwoven strands: the curious things an adolescent girl gets up to when she creates her own web site; the Scottish Parliamentarian, father of the wounded survivor, who is determined to exploit the tragedy for his own ends. Always hostile to the police, his comeuppance will be terrible indeed. In short, the story is as involved and as involving as all its predecessors and should not be missed.

Connelly’s novel is less satisfactory. The plot gives a new meaning to the expression “far fetched”, and the obsessive behaviour of Pierce is wearing and exasperating. It makes no sense at all until far too far into the novel. After breaking up with his partner, who can no longer take his obsessive pursuit of a molecular computer which he and his company are developing, he acquires a new apartment – and telephone number. He is assigned the number of a popular call girl who advertises on a web site. If she has retired why leave her number there? Pierce determines to find out what has happened to her and descends into a milieu he would have done well to avoid. Sex and the World Wide Web are displayed seamy-side up. Pierce shrugs off the warnings of better informed players and plunges on to near destruction.

This book is not easy to review because it is impossible to outline the story without giving away the plot. Suffice to say that things are not quite what they seem and while Pierce appears out of control, his behaviour has been anticipated by others. If the book has a message, it is that obsessive behaviour is not just dangerous in itself, it can be exploited by the unscrupulous. The climax is worth waiting for but it was worthy of a more believable plot.