A READER is warned ahead of time. The title, the formidable contents page with more little gobbets of items than a Chinese banquet, something called "A First Note," and the contorted conditional with which the first Note begins: "The people in this book might be going to have lived a long, long time from now . . ." If it's a water-tight novel you want, this one lets in the rain.

The endeavor is to create not a novel but a world. A fashionable exercise. The world to which that contorted conditional leads lies in Northern California in the far future, after a destructive nuclear war. All that we know has gone, or has been changed. The Indians have their country back.

There are diseases caused by long-term genetic damage wrought by radioactivity. Otherwise, this is a harsh, ascetic pastoral, set in a land where poverty is wealth and animals are also people. Dances are danced for every season, songs sung for every insect. Humans are not just close to nature. They are again part of nature, and that they see visions is taken for granted.

Le Guin's book -- prettily produced with pictures and emblems on most pages -- is stuffed with poems, songs, patterns, maps, dried flowers, feathers, stones and drums. Her folk, the Kesh, scuttle into the shadows as one turns the page.

A cassette of the Kesh's music and poetry accompanies the book, as if the book were not enough.

Among this vernal bric-a-brac are set stories, legends, and tales. The longest story, "Stone Telling," is divided into three parts in order to give some kind of narrative backbone to the book. It relates the life of the woman, Stone Telling, her growing up, her going to live with her father in the military City of the Condor, and of her eventual return to Sinshan, in the Valley. It is unsensational, its explicit anti-military note giving it a bite which some of the short stories lack.

Among the lesser stories, glimpses of the alien in "At the Springs of Orlu," and the visions of "The Bright Void of the Wind" are particularly strong. "The Visionary," too, has true power, rendering the remarkable banal and the banal remarkable.

Such marvelous transformations do not take place as frequently as hoped. Pretentiousness is no substitute. ("Owl hears itself: that makes sound be; sound comes into time then, four times . . .")

Occasionally one hears the dry rasp of the anthropologist's voice. The tone of the superior teacher, present in earlier Le Guin, still echoes here and there. But by and large, this is a deeply worked-for attempt at another world than ours, an insight into what -- with luck -- might be our true natures.

Mutants, dragons, telepathy, and the ghouls in which earlier writers delighted, find no place here. Even the Condors, the baddies, die out. We find the Kesh boring at times -- the fate of quietists. They have no gods, no faith. "What they appear to have had is a working metaphor." That's a bit of a dry crust for people who name themselves after pumas.

It comes as a considerable shock, about a third of the way through the book, to encounter a piece of inventiveness which is new -- or newish -- to the not particularly distinguished genre of post-catastrophe novels.

Mankind's materialist culture has long gone, but communities of computers and cyborgs survive. Eleven thousand such communities across the planet form an intercommunicating entity, the City of Mind. This is explained in a section entitled "Time and the City." Human beings can tap into this City via exchanges, if they so wish.

THE CITY has no ambitions to take over mankind and enslave it; it has its own affairs, and is proceeding with the exploration of space.

Information-gathering is its main function. As far as humanity is concerned, it is neutral. This sort of neutrality, a passionlessness, pervades Le Guin's thought. Here it is effectively embodied.

Le Guin appears in her own book as Pandora, sometimes addressed as Aunt -- very suitably, one might think. Talking to a librarian, she says, "This is the kind of conversation they always have in utopia." Such self-conscious blemishes are rare. On the whole, she sails with flying colors across the tenebrous world of dreams with which science fiction has always flirted. Swallowing the message is another matter. Whether one cares to think of the Stone Age as utopia is a question of personal preference. My preferences are strongly against.

Reading this gallimaufrous book is like tickling for trout. You wait a long time on the bank, patiently. Your hand grows cold in the water. Suddenly, the mysterious creature is there beneath your touch. You pull it out of the stream. You rejoice. You have a feast. But not everyone can acquire the knack.

One of Stone Telling's exasperating little poems comes to mind:

She dances there, she dances there.

She dances where she went

Laughing among the people.

It flashes, it vanishes,

Firelight along the water.