In the author's note to this, his debut novel, David Laskin mentions how his mentor, the late Ivan Doig, "jumped the fence" from nonfiction to fiction midcareer and nudged Laskin to do the same. With three works of nonfiction under his belt, Laskin made that jump. It could have been a disastrous leap into the unknown. However, he was fully aware of where he was going and landed on both feet. "What Sammy Knew" is a hugely accomplished first novel about growing up fast amid personal strife and public upheaval.

The book's eponymous character is 17-year-old Sam Stein. Like his creator, he is raised in Great Neck, Long Island — or as Sam terms it, Fat Neck, Lone Guyland — partly by his parents but mainly by their live-in housekeeper Tutu Carter. On New Year's Eve 1969, just hours away from a new decade, Sam heads to a party and meets two individuals who transform his life. One is Richard Rines, an older, cooler friend he hasn't seen for six years: "The outlaw alter ego Sam wanted to be and be noticed by. Demigod and devil rolled into one." The other is firebrand activist Kim Goodman, with whom he becomes smitten.

First love blooms as the pair spend time together. But following explosive eruptions in their respective homes, Sam and Kim move out and go "underground," taking refuge in Richard's East Village apartment. Sam spends his days either observing the revolution taking shape on the streets or getting to know Tutu's grandson Leon in Harlem. Kim becomes involved with protest movements but gets in too deep when she embraces violence. Richard loses himself in a half-lit world of drugs and booze. Eventually, after having kept away from trouble, Sam realizes to his horror that a dark plot is in motion, one that involves his closest friends and threatens an innocent man.

There is a great deal to admire in this foray into fiction. With wit, acuity and tenderness, Laskin paints a vivid portrait of a young man coming of age. When Sam meets Kim and vaults "from childhood to adulthood in a single bound," he remains naive and blind to dangers and conspiracies around him, and so becomes a deeply sympathetic figure. The characters around him are equally well drawn, and their moment in time — an era marked by hedonism, idealism and radicalism — is skillfully evoked.

The novel is particularly powerful when Sam sets out to hear Tutu's and Leon's life stories. Tutu wonders why no one in Sam's family has ever asked who she is and where she comes from: "I never could figure out if they didn't care — or if they just didn't see me. Like I was part of the furniture I was supposed to dust." Through Leon, Sam learns valuable lessons about privilege and race. We do, too, in this timely and engrossing read.

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

What Sammy Knew
By: David Laskin.
Publisher: Penguin Books, 288 pages, $26.