Mercy, By Jussi Adler-Olsen, trans. Lisa Hartford

The Swedes have had it all their own way for too long in the crime-fiction stakes. The Danes are coming, with the television hit The Killing in the lead. Brandishing the most imposing literary axe is Jussi Adler-Olsen, whose novel Mercy is already a phenomenal success in various languages.

Despite clear congruences between Denmark and its Nordic neighbours, there are striking divergences. Danes pride themselves on being the cultural nexus of Scandinavia, boasting a cornucopia of modern design, tolerance and innovation. But, of course, Denmark is no fairy-tale country. The government is under the sway of right-wing politicians (to the dismay of its more liberal inhabitants, notably in the arts); immigration laws are routinely criticised by the UN; and Denmark is engaged in the Iraq conflict. Copenhagen, like other big cities, has its own problems with violent gangs, prostitution, poverty and drugs.

These currents – the good and the bad - inform Adler-Olsen's weighty and disturbing novel. Mercy deals with corrupt individuals, social outsiders and manipulative psychopaths. The spectacle of the abuse of power in the "perfect" social democracy (not to mention grim visions of torture in this sylvan setting) has a lacerating force.

A kind-hearted reviewer can give very little away about the plot here. Suffice to say that, just when the reader thinks the torments visited on a woman incarcerated for years in a bizarre chamber could not get worse, that's what they do – and with an ingenuity as impressive as it is unnerving.

Mercy sports well-rounded characters (including the obligatory on-the-ropes copper) and a striking premise. The book is about second chances. Carl Mørck once enjoyed the reputation of being a good homicide detective -- one of Copenhagen's finest. Then a bullet nearly puts an end to his career and his life. He survives, but two colleagues are less fortunate, and Carl lays the blame at his own door.

As he begins to go off the rails, the termination of his job is clearly imminent. But to his surprise he is promoted to the newly-created Department Q, designed to deal with "cases of special focus". His ex-colleagues are sarcastic, dismissing it as a repository for hopeless cases. It's felt that erratic Carl is the right man for this non-job. But his first assignment concerns missing politician Merete Lynggaard, who disappeared five years ago and is believed dead. Needless to say, she isn't... at least not yet. And Carl may have found his way back to self-respect.

Adler-Olsen has written four books in the Department Q series, all Danish bestsellers on publication. His real coup in this pitch-black novel is perhaps Mørck's seemingly maladroit assistant Assad, a Muslim utterly lacking in social skills but possessed of astonishing insight. It's the eccentric Assad as much as the over-familiar figure of the burnt-out detective who will have readers hungry for more from Department Q.