When it comes to bestselling fantasy, Veronica Roth is a name to reckon with. Her young adult Divergent series (2011-2013) --- the perilous tale of a misfit adolescent girl in a strict post-apocalyptic society --- was a smash hit. Although intended for a younger audience, the books were catnip for unashamed senior fantasy fans like myself. In fact, I adore all the iterations of the teen-who-saves-the-world theme, from Frodo to the Narnia kids, from Harry Potter to Katniss Everdeen and Roth’s own Tris Prior.

But, as Roth points out in an interview, none of these books have sequels in which you find out what happens after the world is saved and the heroes grow up (an exception is the play “Harry Potter and the Cursed Child”). That’s the goal in her first fantasy novel for adults, CHOSEN ONES.

As the book opens, we find ourselves in the PTSD-ridden, magically endowed, thoroughly gnarly brain of one Sloane Andrews. She is a character as fearless as Tris but also, frankly, a pain in the butt.

Sloane and her four cohorts --- Matthew Weekes, Esther “Essy” Park, Albert “Albie” Summers and Ines Mejia --- were recruited by the CIA as early teenagers. These five Chosen Ones were groomed to fight the malign, mysterious creature known as the Dark One, who generated events that literally tore up the landscape and ripped human bodies apart. Finally, a decade ago, they killed him. A Ten Years Monument in Chicago, the scene of their victory (and Roth’s hometown), is about to be dedicated, followed by a Ten Years Peace Gala.

While Essy, with her own social-media “lifestyle brand,” embraces this opportunity for celebrity, and Matt accepts public veneration with dignity and grace, the others aren’t so happy. Albie has issues with addiction and depression; Ines acts tough but is permanently on edge. And Sloane --- well, she’s always pretty grumpy, and right now she’s also confused about whether to marry Matt, her longtime boyfriend and prospective fiancé. He thinks her hard shell is just a defense; with a little therapy, she’ll get over the trauma of their battle with the Dark One. But Sloane knows her grief, guilt and unease are too deep to be so easily resolved.

"CHOSEN ONES should appeal as much to teenagers as to grown-ups. Both generations, I think, will find much to savor."

The same is true of scarred, sensitive Albie, with whom Sloane has a special bond. When he dies, she is devastated. The Chosen Ones scatter his ashes in the Chicago River, a solemn moment --- and then, BAM!, they’re torn from their current reality and transported to a different dimension.

With this plot twist, the novel comes brilliantly alive. The parallel universe, known as Genetrix, is a weird place: Chicago, yet not Chicago. On Earth the use of magic is occasional, elusive and, for Sloane in particular, destructive (she regards it as a killer “infection,” a concept that couldn’t be more relevant at the moment); on Genetrix it is a pervasive, apparently harmless everyday skill practiced by everyone, channeling magical energy through tools called siphons. (It often seemed to me that Roth is commenting on the way we are both empowered by and addicted to our phones and other devices --- ultimately at the expense of practical know-how.) The ambiguity of magic is a big theme in CHOSEN ONES. No longer a matter of benignly waving a wand or clicking ruby slippers, here is a phenomenon as complex and dangerous as any natural force.

The Chosen Ones (all except Ines, inexplicably left behind) have been summoned by Genetrix’s leaders to fight their own world’s version of the Dark One, the Resurrectionist --- so called because he commands an army of the walking dead (you’re guaranteed to enjoy Roth’s piquant version of zombiehood).

Matt and Essy have little trouble settling in; they start dressing in exotic local threads and become proficient at using the magical siphons. But Sloane, being Sloane, is suspicious. Is this enemy the Dark One reborn? How, exactly, are Earth and Genetrix connected? She reads, snoops, gets captured, escapes and makes unexpected alliances --- ultimately discovering that the Resurrectionist is not what he seems. In the process, she realizes that “knowing magic was about knowing yourself,” expressing your own deepest desires, which in her case are a mix of murderous and merciful. In the end, she finds romance with someone whose magical talents are as massive as her own. The earth may not move when they make love, but random objects in the room skitter around.

A perennial challenge for fantasy writers is how to keep the narrative going while giving the reader just enough information about the world they're building. In CHOSEN ONES, Roth provides context by inventing documents: magazine profiles, government reports, book excerpts, even poetry. Although many of these fictional primary sources are clever, satirical and authentic-sounding, there are a lot of them. At times I felt I was drowning in background material when all I wanted was for her to get on with the story.

But I adored the fabulous, loving detail of Roth’s Genetrix. It feels as though she had a blast creating it. The best siphons, worn most often on people’s wrists and ears and throats, are made by a company named Abraxas (a.k.a. Apple?); they range from simple objects of black metal to higher-status models resembling elaborate jewelry dripping with delicate beaded chains and set with gems. Essy, naturally, is especially taken with trendy Genetrix fashions like blue lipstick, pointy shoes and outfits that are a wild clash of patterns: paisley, checkerboard, stripes, herringbone. As for architecture, although McDonald’s golden arches and some of Chicago’s signature modernist buildings survive, on Genetrix many edifices are a mash-up of different styles: one lobby combines baroque, gothic and art deco. There are also magical skyscrapers that defy the laws of gravity, featuring objects suspended in air with no visible means of support.

So, is CHOSEN ONES really an adult novel? Although Roth clearly intended it to be a departure from Divergent, I must confess that I don’t think it is all that different (the single sex scene wouldn’t even qualify for a PG rating). True, Sloane is no longer an adolescent, yet hers still seems to me a coming-of-age saga. Witness her feistiness, lack of impulse control, shapewear phobia and boot fetish; her sense of being unwanted and manipulated by uncaring adults; her quest for identity. Here is a woman who needs to integrate and transcend the traumatic events that made her a hero --- and now give her nightmares. I rooted all the way for her to find herself, in one universe or another, and, as Roth puts it, to realize “that pain doesn’t give you license to be an a--hole.”

Labels don’t matter; CHOSEN ONES should appeal as much to teenagers as to grown-ups. Both generations, I think, will find much to savor.