The Girl with the Dragon Tattoo, By Stieg Larsson, trans Reg Keeland

If this novel leaves you with a thirst for others by Stieg Larsson, it will be largely unslaked: there are just two more books. Larsson's Millennium trilogy was delivered to a Swedish publisher shortly before the author died at 50 in 2004. Since his death, sales of this novel have exceeded a million in his native country. Larsson was also a crusading journalist, confronting far-right groups and defending the defenceless. Inevitably, he and his partner were threatened by extremists. But Larsson remained unintimidated, and fought for his beliefs up until his death from a massive heart attack.

So what is the secret of Larsson's astonishing posthumous success in Sweden? At the start of this weighty novel, Larsson appears to be testing his readers. He has up his sleeve two extremely engaging protagonists. Once these characters have appeared, our surrender to the novel is guaranteed. Before that, however, we are subjected to lengthy (and impenetrable) details of financial scams in which the reader (like the characters) seems to be being told – sharply – to pay attention. But just as our patience is being tested, Larsson allows us to luxuriate in some impeccable plotting.

The action involves disgraced journalist Mikael Blomqvist and computer hacker Lisbeth Salander. The former is cut from a familiar cloth: the tenacious reporter who has taken on a dangerous enemy (like Larsson himself), but Salander is that rara avis, something utterly new in crime fiction. Much esteemed by her financial investigator boss, Salander belies her professional expertise as investigator by an off-putting punk appearance: facial jewellery, outlandish clothes and the eponymous tattoo. One of her subjects is Blomqvist, sacked after a disastrous legal defeat.

Unaware of Salander's report on him, Blomqvist is hired by an ailing magnate to investigate the disappearance (and possible murder) of his niece on an island. The island was cut off from the mainland by an unlikely accident involving a blocked bridge, isolating a group of suspects. Before the reader can cry "Locked room scenario!", Larsson beats us to the punch, with his characters noting that this is classic English mystery territory. But not for the first time, we're being wrongfooted: what follows is much darker and bloodier – more Thomas Harris than Dorothy L Sayers.

Reading The Girl with the Dragon Tattoo, in Reg Keeland's elegant translation, is a bittersweet experience. We are constantly reminded that an accomplished literary voice has been stilled. For instance, just as we are worrying that Salander might alienate the very people she is plugging for information, Larsson has her remove her face metal and don conventional clothes: she has, in fact, a secret identity.

She is also, despite her insolent manner, vulnerable, tying in to a feminist undercurrent here ("18 per cent of the women in Sweden have at one time been threatened by a man"). But if this suggests a vitiating PC quality, the unsparing horror the novel deals out banishes any such notions.

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