IN MEDIEVAL ARTISTS' representations of tragedy, human fortune turns upon a great wheel. The protagonist is borne as high as mortals may soar, then swung down into the dust. A Theban king blinds himself; a Moorish general kills himself. Our century accredits tragic figures less exalted--the diameter of the wheel no longer matters, though its turn must still be complete.

The people of Ernest Hebert's second novel, which aspires to tragedy, are not brought down into the dust. The dust is where they begin. For them, a safe squalor among one's squalid family is the highest imaginable good.

Beyond this strait world lie mysteries, divinities, and magic: government; religion; television programs; games such as tennis that are so mysterious their meaning is assumed to be sacred.

The "kin" of the novel's title are the Jordans, luminaries of a benighted class known in Darby, New Hampshire, as the shack people. "No kin of mine," says a local sage. "No kin of yours, no kin of God almighty himself. They ain't even a family exactly. . . . Just a collection of like-minded individuals, like communists or participants in modern art."

Though the author looks into everyone's mind (a form of promiscuity that tends to waste the novel's force), the plot chiefly concerns Ollie Jordan, a clan leader. Ollie thinks the Welfare Department is out to grab his idiot son Willow, whom he keeps attached to himself with a chain.

Kicked off the land where he's been squatting, Ollie hauls trash for a living, scavenging what he can. But he slides ever deeper into lassitude, drunkenness, and paranoia. The Welfare Department becomes his obsession; he believes it can read his mind. Retreating to a remote mountaintop, Ollie patches together a shelter of boughs and plastic sheeting, and there awaits his fate.

Intelligent but ignorant, Ollie also patches together, from too few scraps of understanding, a view of the world. Often his thinking reminds us of how we thought when we were children:

"He had overheard the word 'boudoir,' and deciphered that it meant a place for lovers. He had analyzed the word and found it a good one. The meaning of the '-war' part was clear enough, for what were lovers but ceaseless battlers? As for 'bood' -- he figured that was one of the less ugly terms referring to copulation." We recognize this foolish wisdom; we have been this logical ourselves.

Yet it is just here, in the span of Ollie's character, that the novel frequently sags. Too much of the time he is sentimentalized, condescended to. He's made into a fount of folk wisdom: "There ain't no other time but now"; "The more you take from me, the less we both got." Or into a joke of a bumpkin: catching Sesame Street on a tavern TV, he thinks, "Bert, don't take crap from Ernie -- bat him one."

Ollie's thoughts run in sprints and stalls, visions and fugues. At one point he paces, "pondering the problem of how to get a dog, not because he actually wanted a dog, but because it busied his mind." This reduction of thought to a mechanical process largely beyond control rings startlingly true.

When he goes crazy, though, we unfortunately stop believing him. His mental illness is carefully detailed but rarely persuasive. Notions pop into his head from nowhere. A character may be mad utterly, but not arbitrarily: if we can't find his connections (however twisted and frayed) to a mental world we understand, he becomes a string of random signs.

For the larger society surrounding the shack people's, the author has little patience. Its few representatives are caricatures. A social worker finds in Ollie's treatment of Willow "a sad case . . . parenting without goals or objectives." An ass of a college dean, in an intrusive satire of academia, congratulates a professor on "firing culture shots."

One regrets this novel's miscalculations, because at its heart is something solid and touching: the relationship of father and son. Ollie's feelings for Willow are complicated, sometimes unexpected, and tender; Willow's for Ollie are imponderable -- Willow can't speak -- but plainly deep. Though Ollie knows that his son is an idiot, he also suspects that Willow is a genius, one with a wild sense of humor.

This element of the novel is so vital that it's a shame the author piled atop it a carapace of melodrama: Ollie and Willow turn out to be (in addition to father and son) half-brothers. That explains the sly title. Why doesn't Ollie remember siring Willow upon their mother? Because he's suffering from amnesia. Secret consanguinity and amnesia are among the crudest devices of fiction, and unworthy of the much in this novel that's very good.