If you regularly read book reviews, you're probably familiar with the phrase "promising debut." Critics use it as shorthand for a first book that suggests a bright future career for the author, a good initial effort.

Nana Nkweti's short story collection "Walking on Cowrie Shells" isn't that. It's such an accomplished book that it both makes a promise and fulfills it — a debut so audacious and masterful, it's hard to believe it's her first time at the plate.

The stories in Nkweti's book range widely, bouncing between the realistic and fantastic. In "Rain Check at MomoCon," Nkweti follows Astrid, a teenager who aspires to be a comic book writer but knows her parents will never go for it: "Lawyer, doctor, engineer — the high holy trinity of professions blessed by African parents. Writing graphic novels? No. Friggin'. Way."

She tolerates the company of her two "frenemies" because she's constantly "bending and contorting to the will of others in a single fold." But she really just wants to spend time with Young, an artist with whom she collaborates, and whose parents are similarly insistent that he embark on a "respectable" career. The story ends with Astrid asserting herself, uncharacteristically; it showcases Nkweti's compassion and love for the underdog.

Nkweti turns to something approaching fantasy in "It Just Kills You Inside," about Connor, a crisis management expert who's called in to handle an unusual problem: zombies in Cameroon. The undead were the victims of the (real) Lake Nyos disaster in 1986, in which an eruption caused a carbon dioxide cloud that killed hundreds — and in this story, caused the zombification of others.

The twist here is that the zombies are the victims, not aggressors, hunted by vigilantes who incorrectly think they're dangerous. The hard-boiled style of Connor's narration makes it fun to read, and it's a sharp look at crowd mentality and what happens when people refuse to challenge their assumptions: "You have to understand that people wanted to be lied to," as Connor says.

Much darker is "The Statistician's Wife," about an academic "as American as Coca-Cola, and capitalism" being investigated for the murder of his Nigerian spouse. As the story progresses, the reader learns that the statistician — who grew up with a father who rewarded his son for fighting — has grown jealous of his wife's social life, suspicious anytime she leaves the house alone.

Interspersed in the story are brief descriptions of real-life murders of Black women by their partners — the kind of slaying that too often goes unreported by the media. It's a deeply chilling story that doubles as a powerful critique of misogyny, racism and toxic masculinity.

Nkweti has fun with language throughout the book, but that doesn't stop her from being serious when she needs to. It's the kind of high-wire balancing act that's hard for any writer to pull off; that a debut author does so this gracefully is a stunning accomplishment. Anyone who appreciates authentic and original fiction will find something to love here. And that's a promise.

Michael Schaub is a member of the board of the National Book Critics Circle. He lives in Texas.

Walking on Cowrie Shells
By: Nana Nkweti.
Publisher: Graywolf Press, 176 pages, $15.99.