Legend of a Suicide, David Vann's first book of fiction, won a short-story prize in the US, but isn't exactly a story collection  or, for that matter, a novel or a memoir. It might best be described, borrowing from VS Naipaul's rather grand-sounding subtitle for one of his similarly mixed works, as a novella with five "supporting narratives". The first-person stories that begin and end the book provide context and framing for the third-person novella, which turns out to be a fiction within the fiction. To complicate matters further, Vann operates in ambiguous territory with regard to real life. The stories are "fictional", he says in the acknowledgments, "but based on a lot that's true"  principally the suicide in 1980 of his father, James, to whom the book is dedicated. Readers are left to judge for themselves how firm a line to draw between the historical James Edwin Vann and the book's James Edwin Fenn, and between David Vann and Roy Fenn, the narrator-protagonist.

The first story, "Ichthyology", lays out the basic contours. Roy remembers his early childhood in Ketchikan, Alaska, where his father practised dentistry and nursed an idea of himself as a self-reliant outdoorsman. When Roy was almost five, his father came to feel that he had been cheated of experience in the area of women. "My mother was only the second woman he had ever dated," we're told, "but to this list he now added the dental hygienist who worked for him." Roy's mother left with Roy and his sister for California; James had a short-lived second marriage, then sold his dental practice and bought a fishing boat, not learning the ropes first or hiring a captain, which would have undercut his lone-explorer self-image. Two disastrous seasons later, with the taxman closing in and the boat's sale imminent, he walked to the stern and shot himself with a Magnum handgun.

"Ichthyology" registers Roy's distress indirectly through close attention to the fish he keeps in a tank, one of which ends the story by catching a fly, setting off a "million tiny ripples of panic". It's also filled with the kind of frozen detail that tends to stick in the mind after such events (after getting the news, the family drink "clear bouillon soup with a few peas in it"). Most importantly, though, it establishes a tone and a measure of ironic distance from both the speaker's younger self and his father's multiple failings. As in the memoirs of Tobias Wolff, who's also mentioned in Vann's acknowledgments, it's a tone that allows for nostalgic warmth, quietly unsparing judgments and sardonic humour. Vann's skills as a deadpan comic are apparent by page two, which describes childhood fishing trips: "The halibut themselves lay flat, like grey-green dogs on the white deck of the boat, their large brown eyes looking up at me hopefully until I whacked them with a hammer."

Further stories circle cautiously around the hurt caused by the failed father-son relationship. The fullest portrait of James, however, comes in "Sukkwan Island", the novella at the heart of the book, in which Roy, aged 13, agrees to spend a year with his father in a remote cabin in southern Alaska. As Roy half-expects, his father turns out not to have planned ahead very well: their supplies are inadequate, and James's confident talk doesn't hide his lack of know-how. James also has unrealistic expectations of being cured of his unhappiness over the failure of his second marriage by spending time in the wilderness, and becomes morose and self-absorbed. Women never give you a break, he explains; when I caught crabs off a prostitute and passed them on to your stepmother, she wouldn't even give me a chance to explain myself. At night, when he thinks that Roy is asleep, he sobs in his sleeping bag. Roy wants to go home but fears that something terrible will happen if he does.

With its strong focus on fishing, hunting and other manly activities, its deliberately flattened tone and "and"-heavy sentence constructions, "Sukkwan Island" initially comes across as an exercise in neo-Hemingwayesque, enlivened mostly by the father's frequent ups and downs. Soon, though, the reader comes to share Roy's growing sense of dread. Then something happens that I can't describe without spoiling the book, but which makes it clear that Vann isn't merely writing a fictionalised memoir. Without changing the tone or drawing attention to what it's doing, the novella reveals itself as a type of fantasy  vengeful yet sorrowing and empathetic, plausible yet dreamlike, and completely absorbing. Operating at a high level of emotional intensity, Vann triumphantly reels the reader through to the closing stories, in which an older Roy returns to Ketchikan, bringing the book full circle.

Legend of a Suicide benefits greatly from its Alaskan settings: the striking backdrops, the isolation, the emotion-bearing marine imagery. (Roy grows up to be a fan of Elizabeth Bishop's animal poems.) It's also very cleverly constructed, but isn't in love with its cleverness; raw yet controlled feeling is what's aimed for and achieved. Moving, readable and often bleakly funny, it deserves to find a wide and enthusiastic readership. Its UK publisher's comparisons with the likes of Wolff and Richard Ford aren't, for once, misplaced.

Before reading David Vann's book, there are three things you should know. The first and most important is that, though this is a work of fiction, the suicide of the title was a real one. The sombre American edition (it came out in the US earlier this year) makes this explicit, up front, in a note on its inside flap. The British edition, however, omits that note. Vann's dedication remains  "For My Father, James Edwin Vann, 1940-1980"  but it is now left to the author's acknowledgments at the end to remove any ambiguity over the fact that his father killed himself.

For sure, it would be an odd reader who had not already come to this conclusion, but it needs to be stated from the outset. There must be no ambiguity, because unless this is clear, the far more profound and shocking ways in which Vann goes on to break with actuality may be muddled and diminished.

The second thing you need to know is that this is a collection of stories and not a single narrative. There are several incongruities in the way the British edition of Legend of a Suicide has been published  packaged between whimsical covers that present Vann's jagged, desperate act of existential mastery as if it were a flight of magical realism, describing his howl in the dark as a "tender story of loss, survival and disillusioned love". But there is a more serious distortion. Inside this edition, Vann's series of five short stories  and one long one  is made to appear as if merged into a continuous novel, with numbered chapter headings.

This has presumably been done on the assumption that British readers are less likely to buy collections of short stories. The result, however, damages Vann's endeavour, which is to change, from one story to the next, not just perspectives, but events themselves. His fictional alter ego, Roy, is present throughout the book, but in radically altered circumstances. The blurb on the cover says that Roy's father kills himself on the deck of his boat, which is weirdly misleading. This happens in one story, but not in another.

There is no single death. Though all the stories are connected, there is no single story. The power of Vann's "legend" emerges from the way a real-world event is imagined, changed and reimagined as if it were taking place over and again, in parallel but contradictory worlds.

Then there is the third thing you need to know which is, rather, something you must not know. As this book reimagines its central death, an event occurs that utterly transforms the encounter between protagonist, father, author and reader. Do not let anyone tell you what this event is before you start. To know what happens in advance would be to spoil not just a narrative surprise in a heart-thumping tale, but the entire apparatus Vann has constructed to wrench out the dreadful and meaningless facts of existence, to master them, and, in a violent act of fictional transmogrification, to reconfigure them as something not less, but more real.

David Vann is a young American author whose first book was a memoir, A Mile Down, about how a boat he had built sank in the Caribbean, in a peculiar echo of previous family accidents. He might also, here, have written a memoir of his father's suicide, but such a memoir, however direct, however honest, however lacerating, could never have reached the psychological depth, the real-world knowledge, of the fiction that he has produced instead.

With his opening story, "Ichthyology", Vann unveils Roy's Alaskan family background, some of his father's failures, one account of the suicide, and inserts an eerily symbolic description of silver-dollar fish sucking out the eyes of an iridescent shark. The details feel acutely true, both literally and emotionally, but apart from the one biographical fact you know about Vann, you have no idea precisely what has been recorded and what has been invented. The feeling of memoir metamorphosing into fiction cocoons an entire sense of reality as Roy investigates his mother and father, their divorce, his stepmother and his father's infidelities. Roy explains himself with a taut and quivering emotional control which at first merely hints at, and only occasionally lurches into, the psychological wilderness surrounding everything.

And then in the central story (or novella) of the book, "Sukkwan Island", that wilderness opens up. A 13-year-old Roy is taken to a remote Alaskan hut by his father and it becomes clear that the father is using the son in a desperate, last-ditch attempt to rebuild his life and stave off the encroaching dark. Roy listens in the night as his father weeps, cringes, confesses his sexual cravings, jabbers his delusions, begs his son for forgiveness. Roy does not have the mental equipment to interpret this, nor is there another soul for miles around. Psychological and physical survival become the same thing.

Without striking any hysterical notes, Vann's writing gradually marks out a score of unholy human pain. There are hints of Hemingway in the control of the style, but the tide and undertow of its meaning are Dostoevskian. Father and son cannot leave this place. You, the reader, will not be able to leave it either.

Vann inhabits and possesses his father's shame-diseased, dying, subjective experience, claiming it  appallingly  as his own. You draw breath at the daring of it. The stakes are high and serious. There is no border here between external and internal realities; this is a book that must already have changed things in the author's world. What of Vann's family? What of his mother? What of the other women in his father's life, whom he evokes and implicates and hands over to the reader for judgment? Are they also his to possess?

Legend of a Suicide is a book that exists in what may be the last taboo region of literature. When another American writer, James Frey, published a furious memoir of his struggle with addiction  A Million Little Pieces  he was pilloried and discredited by American critics and readers, Oprah Winfrey, most notably, after it was discovered that he had been dishonest with his facts.

When Michel Houellebecq's mother disowned him for producing what she saw as a travesty of her real self in his fiction, Houellebecq retreated into the French role of the amorally licensed artist. When, more recently, novelist Julie Myerson produced a literal account of her son's drug use, the British reaction was dominated by critics who declared that it was a story that should not have been told.

These are examples of fictionalised memoir, fiction exploiting elements of memoir, and memoir that would have been safer as fiction. The extreme reactions to them were defined by the way they put an idea of the real under threat, exposing and tampering with inner lives, not just inside a book, but in the world.

Vann goes beyond such distinctions. His legend is at once the truest memoir and the purest fiction. You need to know it is based on facts to understand just how far he has gone in creating a new reality. But you also need to remain ignorant of the fictional surprise he has in store, so that it can hit you with the full force of new knowledge. Nothing quite like this book has been written before.

David Vann writes about fishing with his father in Observer Sport Monthly

Alexander Linklater is associate editor of Prospect magazine.