“I would always have something to prove,” the narrator of Yaa Gyasi’s new novel says. “Nothing but blazing brilliance would be enough to prove it.”

In such passages of mingled frustration and determination, one senses an element of autobiography.

When she was just 25, Gyasi reportedly sold her debut novel, “Homegoing,” for $1 million. It was the kind of financial windfall that whips up fawning publicity and — despite the book’s success — skepticism.

If there are any skeptics left, they can stand down now. “Homegoing” wasn’t beginner’s luck. Gyasi’s new novel, “Transcendent Kingdom,” is a book of blazing brilliance. What’s more, it’s entirely unlike “Homegoing.” That debut, as many fans know, is a collection of linked stories that sweeps across four centuries with a vast group of characters in ever changing settings. In a completely different register, “Transcendent Kingdom” is still and ruminative — a novel of profound scientific and spiritual reflection that recalls the works of Richard Powers and Marilynne Robinson.

Not that there’s anything derivative about this story. Indeed, Gyasi’s ability to interrogate medical and religious issues in the context of America’s fraught racial environment makes her one of the most enlightening novelists writing today.

The narrator of “Transcendent Kingdom” is a young neuroscientist at Stanford, a Ghanaian-American named Gifty. Wholly obsessed with her job, she maintains no social life, almost no life at all outside the lab. Her research involves studying the brains of mice. She has devised a behavior testing chamber with a lever that sometimes delivers a tasty treat and sometimes delivers a painful electrical shock. “The mice just had to decide,” Gifty explains, “if they wanted to keep pressing the lever, keep risking that shock in the pursuit of pleasure.” Most of the rodents eventually, if reluctantly, learn to avoid the lever and give up on the promise of special treats. But she’s interested in “the final group of mice, the ones who never stopped. Day after day, shock after shock, they pressed the lever.”

The placid surface of Gifty’s professional life betrays none of the intellectual and emotional torment she relays in the lines of this urgent novel. Although she’s reluctant to tell her colleagues, her older brother struggled for years with substance abuse. The novel's most painful sections — told in poignant flashbacks — explore the interwoven strands of grief, anger and shame that Gifty felt as her beloved brother succumbed, rallied and succumbed again.

Those memories keep reasserting themselves because the data Gifty is collecting in the lab could someday lead to an effective diagnosis and treatment of addiction. But she rejects the sentimental connection she knows colleagues would draw between her research and her brother’s agony. “The truth is I’d started this work not because I wanted to help people but because it seemed like the hardest thing you could do, and I wanted to do the hardest thing,” she says. “I wanted to flay any mental weakness off my body like fascia from muscle.”

What exactly, though, is “mental weakness”? And to what extent does one’s psychological stamina, one’s resistance to addiction evince a moral quality? What, in other words, makes the human animal keep pressing that lever, despite the pain, the risk of death? These are complicated problems, especially for a neuroscientist who, like Gifty, was raised in an evangelical home. “Do we have control over our thoughts? When I was a child this was a religious question,” she says, “but it is also, of course, a neuroscientific question.”

Two thousand years before psychotherapy and brain scans, St. Paul noted the abiding paradox of human behavior when he confessed, “The good that I would I do not, but the evil which I would not, that I do.” Naturally, though, the potential insights of sacred texts have no place in the Stanford lab. Gifty’s colleagues are confirmed atheists, as unlikely to consider the action of sin and God as they would the influence of time travel and elves. Gifty may have lost her belief — driven away finally by the church’s sanctified racism — but she finds her fellow scientists’ disdain irritating and blinkered. She retains an appreciation for the beauty of the Bible and even for the persistence of faith. She understands that science and religion endeavor to answer transcendent questions, but when it comes to the holy nature of her work, she feels the narrow-mindedness of both sides. “The Christians in my life would find it blasphemous,” she says, “and the scientists would find it embarrassing.”

This tension is embodied in Gifty’s relationship with her mother, which is the abiding focus of the novel’s hushed present-day action. In the opening pages, her mother suffers a debilitating relapse of depression, and Gifty takes her in. It’s a plan inspired by love but fraught with contention — disagreements that cause Gifty to reconsider her life and the tragic events that brought both of them to this point.

Though almost comatose, Gifty’s mother rejects any psychological or psychotropic treatment, convinced that only prayer can save her. At times, that radical position feels like a repudiation of everything Gifty hopes to accomplish in the lab, but she’s as moved as exasperated by her mother’s stubborn faith. Her hunger to understand what happened to their family, Ghanaian immigrants in Alabama, draws us through a conspiracy of poverty, racism and addiction that crushes so many in America.

A double helix of wisdom and rage twists through the quiet lines of this novel. Striving to work out the problem of being in the world, Gifty knows there’s no easy way to reconcile her brother’s ordeal with a loving God, a pharmaceutical industry dedicated to healing or a nation based on equality. Her devout mother and her cerebral colleagues both preach a kind of evangelicalism that frays at the outer limits. “This tension, this idea that one must necessarily choose between science and religion, is false,” Gifty says. “Both became, for me, valuable ways of seeing, but ultimately both have failed to fully satisfy in their aim: to make clear, to make meaning.”

For that, thank God, we have this remarkable novel.

Ron Charles writes about books for The Washington Post and hosts TotallyHipVideoBookReview.com, which turns 10 years old this week.

Transcendent Kingdom

By Yaa Gyasi

Knopf. 288 pp. $27.95