A Swedish mystery whose arrival was heralded with glowing reviews, crime fiction awards, and blockbuster sales at home, “The Girl with the Dragon Tattoo” (Knopf, 480 pages, $24.95) cannot help but be something of a letdown to hard-core fans of the genre, even as its unorthodox nature may draw in readers not traditionally gripped by the strictures of a mystery plot.

Faithful readers of the Swedish mystery mastermind Henning Mankell may be reminded of the first time they cracked open an Åke Edwardson or Håkan Nesser book: the pleasurable sinking in to the cold Swedish landscape, the starkness of the crime scene, the introduction to the stoic Scandinavian police inspectors Winter and Van Veeteren, at first so like Mr. Mankell’s Kurt Wallander.

But the quality of the works of Messrs. Edwardson and Nesser is diminished by their similarity to the incomparable Mr. Mankell. Not so for Stieg Larsson, whose first crime novel to be published in America hews to few of the conventions of the genre.

For starters, the protagonist: No police inspector, Mikael Blomkvist is a crusading financial journalist on trial for libeling a titan of Swedish industry, Hans-Erik Wennerström. Blomkvist’s reputation in tatters, and the magazine he founded in danger of closure after an advertiser boycott, he is invited unexpectedly to the home of the reclusive Henrik Vanger, an octogenarian whose once dominant family corporation has been diminished after a series of financial losses. Intrigued but suspicious, Blomkvist is offered the chance to solve a Vanger family mystery, the disappearance 40 years earlier of Henrik’s favorite niece, Harriet. To sweeten the deal, Vanger offers the journalist an exorbitant fee and a chance to bring down Wennerström.

Blomkvist, newly sentenced, reluctantly agrees, and spends a year, hermit-like, in a cottage on the Vanger family’s windswept island in the north of Sweden, puzzling over Harriet’s fate. Along the way, he is helped by a decidedly odd research assistant, 24-year-old Lisbeth Salander, the girl with the titular tattoo. Painfully thin and antisocial in nature, but with a photographic memory and a zest for hacking, she provides him with invaluable clues and, of course, company in bed.

Larsson died at 50, in November 2004, before the publication of “Dragon Tattoo” and its explosive popularity. A crusading journalist in his own right, Larsson wrote his mysteries for fun, in his free time. His fight was against racism and right-wing extremism, and he manages to weave Sweden’s Nazi past into the Vanger mystery by popping a few fascists in among Henrik Vanger’s brothers.

And along with finance, the author elevates violence against women to a central theme: “Men Who Hate Women” was the book’s original title. Hardly ever completely absent in detective novels, such abuse rarely has been met with such an unexpected avenging angel as Salander, whose entire presence alongside Blomkvist, somewhat quixotic until late in the novel, is justified by her furious response to a particularly vile killer.

While Larsson’s central mystery may be a traditional one — “locked room” format, as Harriet disappears on an island whose only bridge is blocked on the day of a Vanger family meeting, leaving a conveniently fixed number of suspects — the amount of space devoted to side plots may frustrate fans of more conventional mysteries. The typical plot arc of discovery of body and introduction to protagonist, followed inexorably by investigation and denouement, is missing here. Essentially, “The Girl with the Dragon Tattoo” has two major story arcs: the first the Wennerström affair and Blomkvist’s magazine, Millennium, and the second the disappearance of Harriet Vanger. When the Vanger mystery is resolved, it’s back to Wennerström and his corrupt dealings for another 50 pages.

Your correspondent, at this point, must confess to being an inveterate, even rapacious, reader of mysteries. So the first 60 pages of Larsson’s book were slightly vexing: Where was the body? But the book picks up speed quite nicely after the Vanger plot line is introduced, and in the end the financial crime aspect is a valuable, if not completely seamless, addition.

The book, with its journalistic tone and twin plot threads, is intriguing enough that it will leave some readers wanting more, and they will get it: Two other Larsson novels are forthcoming in what’s now known as the Millennium Trilogy, and a Swedish movie adaptation is in the works as well.

mmercer@nysun.com