MADDADDAM. By Margaret Atwood. Doubleday. 394 pages. $27.95.

In the Renaissance, Margaret Atwood reminds us, mapmakers drew monsters along the edge of the known world. It is this monstrous space that fascinates her: a territory just over the edge and into the unknown.

“MaddAddam,” Atwood’s latest foray into speculative regions, is the final volume in a trilogy she began 10 years ago.

As she did in this book’s predecessors, “Oryx and Crake” (2003) and “The Year of the Flood” (2009), Atwood splices scenes from the past with scenes from the present. In this telling, the apocalypse has already happened, and menace, in retrospect, was always close, ready to trespass on every asylum. Only the guileless aren’t in on the game.

Leading up to the Waterless Flood (a euphemism for a pandemic that almost wiped out the human race), the situation is dire. Brainiacs wall themselves off in corporate compounds, while “neuro-typicals” run amok in the racy and lawless “pleeblands.”

Corporations rule, as nations once did. Genetic experimentation is rampant, most of it aimed at the immortality industry. Ecologically, there’s trouble: Eastern cities have drowned, the Everglades have burned, and Texas has dried up and blown away.

Atwood begins “MaddAddam” with a crib sheet to bring readers up to speed on the trilogy. The events of volumes one and two happen simultaneously. “Oryx and Crake” centers on the rivalry between two friends who grew up at the HealthWyzer compound: the brilliant geneticist Crake, formerly known as Glenn, and his friend Jimmy, whose gift for language is unvalued.

Crake turns his impressive neuron power to the Paradise Project, a top-secret plan that creates a race of mutants. The Crakers are gentle, insipid creatures. Crake programs them to die automatically at 30 without illness or foreknowledge. Lacking the friction of mortality or the tensions of jealousy and love, they are unpromising placeholders for all the mess and longing that perishes with the human race.

In “The Year of the Flood,” Atwood takes us to the pleeblands and into the heart of resistance against the Corps. She places us among God’s Gardeners, a splinter group of green separatists who worship and follow the teaching of Adam One.

“MaddAddam” picks up right where the plots of its predecessors end, with a scrappy little group of survivors.

Jimmy the Snowman, who thought he was the last man standing in “Oryx and Crake,” is back. So are the Crakers, whom he led out of Crake’s Paradise Dome.

Ren and Toby, who alternated chapters in “The Year of the Flood,” are still alive, along with a congregation of evacuees from the AnooYoo Spa, Scales and Tails sex club, Gardener compounds and the MaddAddamite (counter-terrorist) cause.

Zeb, Adam One’s renegade brother, is a key player, and Toby’s love interest. Shadowing the good guys are a couple of very bad Painballers (convicted murderers who duel to the death with upper-echelon Corps as spectators).

Atwood stages “MaddAddam” as a medley of stories, some of them oral, others written. Toby is our main conduit into these narratives. We are witness to her monumental effort to exist on a human scale and to retain or recover all the dispersed pieces of her own life and of her lost civilization. The vivacity of Toby’s story, and our sense of a richly textured imagination, is a statement of faith and hope. Against the science of genetic engineering, the waste of the environment, the greed of the powerful, the degradation of the lowly, and the general sense that nothing existing was good enough to last, Atwood places the power of the Word.

Much of the novel’s backstory comes to us through Zeb, who recounts his past to Toby, often as they’re in bed together. Toby is an oral narrator herself as well. Every night, she tells a bedtime story to the innocent Crakers.

A benign mythmaker, she creates a clean plot for their untainted minds. As she thinks, “There’s the story, then there’s the real story, then there’s the story of how the story came to be told. Then there’s what you leave out of the story. Which is part of the story too.”

Atwood’s story is many things. Certainly, it’s a cautionary tale that stands at the intersection of several current trends. Atwood says as much on her acknowledgments page: “Althougth “MaddAddam” is a work of fiction, it does not include any technologies or biobeings that do not already exist, are not under construction, or are not possible in theory.”

The data are sinister, but Atwood is also very funny in a punning, satirical way.

“MaddAddam” is, further, a commentary on history and myth and on the reconstruction that converts fact into legend. The Crakers are neonates, in love with their own origin story. Toby curates the race’s memories for them. In the end, her journal stands as a kind of Craker bible.

More than anything, “MaddAddam” is a prospectus for the good life and a statement of faith.

In this version, Atwood imagines a reign of inter-species cooperation and a wide-open call for those traits bred into the Crakers: kindness, especially, and communal care.

Most movingly, Atwood’s good life includes several love stories: Zeb’s for his brother Adam One, Zeb’s for Toby, and Toby’s for Blackbeard, the sweet Craker child who carries on her tradition of storytelling.

Love is the radical opposite of isolation and greed. Bravo to Margaret Atwood for including it among the sturdy values that can survive even a waterless flood.

Reviewer Catherine Holmes teaches English at the College of Charleston.