Los Angeles: 2050 : IN THE HEART OF THE VALLEY OF LOVE, <i> By Cynthia Kadohata (Viking: $20; 224 pp.)</i>

If we could read ahead in the story of our city--lately so besieged by fires, floods, drought, “civilian uprisings,” dirty skies and a trembling earth--what would we find? Is El Grande coming to knock us into the Pacific? Will the Revolution--or an epidemic of smog-related cancers--get here first?

Writer Cynthia Kadohata, who has set her second novel, “In the Heart of the Valley of Love,” in Los Angeles at the midpoint of the next century, imagines the contrary: The city might just limp on the way it’s going, suffering a slow leak rather than a big bang. Like a tanker truck hanging half off a freeway overpass (her book’s opening image), it might flounder indefinitely, on the brink of collapse, its desperate citizens surviving any way they can.

In recent years, a number of novelists have envisioned a future for the world from the vantage point of a troubled present. Denis Johnson’s “Fiskadoro,” Carolyn See’s “Golden Days” and Margaret Atwood’s “The Handmaid’s Tale”--as different as they are--all concern life after some sort of Armageddon, and mix a message of hope with their futuristic horrors: The human spirit, however crushed, reduced or imprisoned, will rise again.

Though Kadohata’s novel ends on a small, faint note of optimism, the pre-fall world she portrays appears too far gone for salvation. Nothing short of catastrophe--a total tear-down of the weak and dying culture--would have any real effect.

L.A. in the 21st Century is a society in pieces, without families, values, government or effective laws to hold it together. Everyone carries a gun. No one (including those who live in gated communities, now called camps ) is safe from muggings, roadside shootings or the police. Corrupt officers routinely make random arrests, reasoning that law-breaking is rampant anyway. Parents can’t protect their children; grown-ups disappear or die young. Seventy percent of women under 40 have cervical cancer. Southland air has grown so lethal that everyone else has a disfiguring skin disease.

Meanwhile, the Century Freeway is still not finished, but it’s surrounded by the ghostly concrete “rainbows” of the “Sunshine System,” a half-built transportation network that died, with the economy, early in the century. Water and gas are permanently rationed, and the gap between rich and poor is so wide that riots break out almost every day. Their aim, logically enough, in a place where no one is responsible and the government has little effect, is destruction rather than change, an ideal that long ago expired from its own weightlessness.

In this nightmarish atmosphere, disgusted, struggling Angelenos feel that life would be better anywhere other than in their own city. They say, “If the riots get bad this year, I’m moving to the country.” And yet they stay. Why do they stay? (Why do we all stay?) Because, declares one very disciplined, unsentimental ex-gang member: “It’s my home.”

A particularly intense blend of beauty and brutality, deprivation and excess, this L.A. is a fitting stage for a futuristic drama of disintegration and vague but persistent hope. As the whole world is falling apart, it’s an accomplishment to survive in the screaming heart of chaos and extremes--on the warlike freeways, in the icy or burning desert, in broken-down Hollywood, where 100 panhandlers sometimes march together in the streets.

What makes Kadohata’s vision so chilling is that it’s not a stretch. Any Southlander who drives, breathes and reads the newspaper can extrapolate from our unwieldy, problem-ridden city to the state of things in Kadohata’s future. There are no androids here, no space invaders, just latter-day incarnations of ourselves who have learned to live with more fear and less of everything else.

With all its dark themes, the novel is buoyed up by the pluck and grit of its narrator, Francie, a 19-year-old orphan of Japanese, Chinese and African-American extraction. She’s a down-to-earth guide, devoid of self-pity, heroic in her willingness to love others despite the loved ones she’s lost, and she survives on a mix of cunning, hysterical humor and cockeyed self-questioning. Like the other battered but gutsy young people around her, she carries fragments of the past with her in the form of memories, which nourish the present and inspire her, and she creates a de facto family out of the raggedy staff of a campus newspaper she writes for.

The novel’s story--if it can be called a story--takes a slice of Francie’s life, from her stepuncle’s disappearance to her decision to move in with her boyfriend. There’s an aimlessness and fragmentation to Francie’s existence, which is echoed in Kadohata’s loose, free-associative narrative structure. The writing is spare but luminous, like the landscape that emerges so palpably from these pages as “a cage of light,” a place where “clouds and mountains glowed like faded neon” and “twirling freeways circled the city like a carousel.”

Binding the separate parts and running through the book like musical refrains are recurrent themes (concerning, among other things, human connection, moral responsibility and suffering) and story lines, some relating to the newspaper, some to Francie’s effort to make sense of life. Colorful characters come and go: Carl, the philosophical tattoo artist; Jewel, the wisecracking managing editor of the paper who’s addicted to an abusive boyfriend; Francie’s part-time employer, an oily lawyer who rubber-bands his glasses on and suffers from self-doubts concerning his flagging client list (“Can I really help them? Can I?”).

Kadohata, author of “The Floating World,” a haunting novel about a Japanese-American girl’s coming of age in the 1950s, is masterful in her evocation of physical, spiritual and cultural displacement. In her new novel, she has written a cautionary tale that is nevertheless sweetened by the transcendent passions of youth. “Don’t forget anything that happened this year, or any year ever,” Francie’s teen-age cousin tells her, in a fit of heartbreak over a boy. “Remember every sad and happy thing, because it’s who you are.”

The message of this marvelous though often painful book is that our capacity to feel deep emotion--our own and others’--just might bind us together, and save us from ourselves.