BY PAGE three of Dirt, one is deeply embedded in its claustrophobic effect, hyper-aware that its damaged characters are doomed. In oppressive summer heat, 22-year-old Galen is feeling stifled by his over-intimate mother: by her offers of tea, by her snuffly kisses on his neck, by her very being. He is still living with her in his rundown childhood home on an old walnut farm in suburban Sacramento.

Galen has every day decided to leave and has every day ended up staying. And it seems the reader will be similarly trapped, not due to inertia, like Galen, but an active desire to follow these characters, no matter how unlikeable, to their ultimate fate. Instead, as David Vann steers Galen's behaviour towards the absurd rather than the disturbed, there comes a point where one might well abandon them.

Vann immediately establishes Galen as an extreme incarnation of solipsistic youth, obsessive and egocentric in his search for transcendence. His desperation to cast off his bodily needs are manifest in his attempts to deny hunger and sexual desire, but he is unable to transcend them, particularly the latter with his provocative younger cousin, Jennifer, playing a vicious tease. Most of all, he wants to be free: of his family and the physical world. Vann has Galen struggling to make sense of a jumble of Buddhist and new-age philosophy, with glimpses of sense among the confusion. It becomes increasingly apparent, though, that Galen is not just confused but crazed.

His emphatically female family - mother, grandmother, aunt and cousin - is marked by Galen's deceased grandfather's abuse of his wife. His mother and aunt battle over the truth about the past, full of resentment over favouritism and money. With Galen's grandmother retrieved from her nursing home, the five go to their cabin in the woods and both family tensions and Galen's losing battle for transcendence are intensified. When his mother finds Galen and Jennifer in flagrante delicto, the doomed attempt at happy families ends.

On return to the farm, it is just Galen and his now wrung-out mother. Undercurrents flare into direct conflict. Until now the tension has built perfectly. But at some point during the long final scene (almost half the book), Dirt tips over the edge into an unwelcome absurdity. Galen's descent into full-blown madness parallels the book's descent into this absurdity.

It's not simply that the plot stretches credulity - many do and Vann has enough talent that he could have carried it off. But now Galen, as he has done before, tries to find transcendence in dirt, whether through covering himself in it or digging it as a meditation, or meditating on it less physically and more cerebrally. This becomes ridiculous, especially after the realism that has preceded this scene. Any empathy one might have had for Galen disappears. Again, it is of course possible to keep a reader engrossed in a repellent character, but it just doesn't happen here.

The novel's failings are particularly disappointing because Vann promises so much, not just at the start here but more generally as a writer. His first fiction, Legend of a Suicide, kept the reader ensnared in its tragedies throughout.

There is still much to admire. Galen is a unique creation. Vann never allows us to be sure where Galen, or the book, will go.

Although the focus is so squarely on the characters, the two main physical settings, farm and cabin, are almost tangible. The rows of old walnut trees on the farm rise before you; you climb the steep paths and plunge into the chill stream with Galen. Butthe other characters lack the substance of that scenery.

Some books grow on you. This one shrinks.

■ David Vann is a guest at the Melbourne Writers Festival. Jane Sullivan is on leave.