Some debut novels are slow burns that subtly flicker to life and stealthily catch fire. Gabriel Krauze's first work of fiction is a markedly different affair, one that gets off to an explosive start and maintains its blistering momentum throughout.

Longlisted for the 2020 Booker Prize, "Who They Was" is a gripping and uncompromising first-person account of a young man with a foot in two disparate worlds. With his parents and at university he is Gabriel, a bad son but a good student. With his fellow gang members on the streets and in the tower blocks of north London he is Snoopz, a law unto himself and a menace to society.

The book's breathless opening scene sees a balaclava-clad Snoopz and his partner in crime Gotti mugging a woman on her doorstep before making off in a getaway "whip." This is no first-time offense. Snoopz does "moves and madness" on a regular basis — robberies, drug deals, stabbings — and without remorse.

Big D pays him "p's" for his efforts. Uncle T gives him a room on the top floor of Blake Court, "a proper crack block." He ups his game and gets a 9mm gun — "my burner, my strap, my mash." He mixes with nittys, shotters, youts and eaters. He breaks hearts, ruins lives and strengthens his reputation.

When he isn't causing havoc as Snoopz, he is displaying his academic ability as Gabriel, impressing his professors with his thoughts on revenge in "Romeo and Juliet" or the morality of murder in "Hamlet." Despite his aptitude for it, English literature isn't thrilling enough to make him mend his ways. "I want to run from the law and feel my heartbeat making me sick," he says. "I want to live dangerously, on the edge of existence."

But that way of life is threatened when he is arrested and put in "pen." It isn't long before he is hit by a sobering realization: "somewhere out there," he declares, "I have lost a part of myself."

Some readers may be skeptical about a protagonist whose dual identity is made up of two extremes. Krauze's novel, however, is autobiographical. He grew up in London in a Polish family and was drawn into the city's gangland underbelly. After studying literature he turned his back on crime and embraced creative writing. His tale of unlikable people doing unspeakable things won't be to everyone's taste. The rest of us will relish its dark energy and brute force, along with the jagged rhythms of its prose.

"Who They Was" might feel like an update of "A Clockwork Orange," with Snoopz and his mandem and their brand of argot and ultraviolence replacing that of Alex and his droogs. But as Krauze's book is based on his own experiences, it feels truer to life — what Snoopz would call "forreal." It is a harsh, yet mesmerizing portrait of a world of "sharp edges and broken things."

Malcolm Forbes has written for the Times Literary Supplement, the Economist and the New Republic. He lives in Edinburgh, Scotland.

Who They Was
By: Gabriel Krauze.
Publisher: Bloomsbury, 336 pages, $26.