Nan Talese/Doubleday.

434 pp. $26.95

We Praise the tiny perfect moles

That garden underground,

The Ant, the Worm, the Nematode,

Wherever they are found.

And the featured soloist was the lyricist herself, Margaret Atwood, renowned more for her 40 works of fiction, poetry, and essays than for her singing, or song-writing, abilities.

The occasion was a "literary performance" of her latest unnerving accomplishment, The Year of the Flood, in which a "Waterless Flood," traveling "through the air spreading germ-ridden mobs, terror, and butchery," doesn't so much obliterate the Earth's social fabric as confirm that it's already torn asunder.

Mother Nature, in tatters, sustains only a patchwork of ragged dystopias. There are the Gardeners, from whose Oompa-Loompa-like hymns comes the mole verse; the HelthWysers, with their yuppie fitness centers; and Pleebland, a lawless sprawl overseen by the crooked CorpSeCorps.

Each entity espouses an extreme ideology, and those who must live by their promises and threats compete for survival in a tale by turns fearsome, busy, heartbreaking, and, like Atwood's invention of a few years ago, the autograph machine, which allows an author to sit at home and sign books at a distant location, a little too glib for its own good.

"Inventing a universe is tough work," writes Nebula Award-winner Ursula Le Guin, and though the term science fiction might seem quaintly outdated now that so much mainstream fiction turns a scientific eye on the fate of humankind, Atwood scores a 10 when it comes to creating, from the stragglers of the old one, a whole new world.

As in Oryx and Crake (2003), in which this vision of Earth first appeared, she peoples it with characters whose scary dilemmas only gradually elicit our full involvement. Jumping between the weeks after the flood and the 25 years preceding it, the story opens with Toby, a designated "Eve," sighting just three pigs in her search for survivors.

Meanwhile, Toby's pupil, Ren, remains locked in the "Sticky Zone" of a nearby "secs" club by turns abandoned and vandalized by murderers.

Distractingly, before their stories take off, Atwood lays down facts as if composing a primer instead of a novel, front-loading so many vocabulary lessons you might despair of her characters' ever becoming flesh enough to fill the atlas assigned them.

The lessons are vintage Atwood, and if the names of the spliced-up fauna, the bobkittens and liobams, amuse you, then the name of the fringe religion, the knownfruits, will have you laughing aloud. Such cuteness almost hijacks the plot, as Atwood's virtuosic satire nearly trumps her compassion.

But finally, and wonderfully, Atwood's warmth prevails. Toby, Ren, and their lost-soul friend, Amanda, would be sympathetic characters in any setting. That Atwood conjures them into this madcap setting, where vultures open "like black umbrellas," misdeeds are punished by kidney removal, and bracelets are made of jellyfish, makes us love them even more.

Never apolitical, Atwood turns her fiercest eye here on the environment, urging readers to contemplate the catastrophes that will befall it if we continue on our current paths. In this message-making mode, she has launched the aforementioned blog of her green book tour, tweets thrown in along the way, swearing to follow "the VegiVows for the duration," requesting that "event venues . . . serve only shade-grown coffee," and promising to use "organic cotton only for the items in our . . . store" and to "avoid bottled water."

Unfortunately, Atwood's online Twitter presence subjects us to: "Got pink hat @ Madison Ave street market," and "Tomorrow I'll do the first-ever reading . . . choosing pieces . . . appropriate for the venue. What might those be? We will see."

Still, Atwood's medicine is good for us no matter how we take it, so even if you're not wowed by The Year of the Flood, you might at least follow her example and "carbon neutralize . . . travel [and] go by train when possible." For, as the blog advises, reducing this sad but exhilarating book to its crucial Cliffs Note: "You only get one chance, and if your heart is not pure it won't work."