In 1973, the first chapter of an unpublished novel was photocopied and passed around the New York offices of Doubleday & Co. with a note. “Read this,” it dared, “without reading the rest of the book.”

Those who accepted the challenge were treated to a swift-moving tale of terror, one that begins with a young woman taking a postcoital dip in the waters off Long Island. As her lover dozes on the beach, she’s ravaged by a great white shark.

“The great conical head struck her like a locomotive, knocking her up out of the water,” the passage read. “The jaws snapped shut around her torso, crushing bones and flesh and organs into a jelly.”

Tom Congdon, an editor at Doubleday, had circulated the bloody, soapy excerpt to drum up excitement for his latest project: a thriller about a massive fish stalking a small town, written by a young author named Peter Benchley.

Congdon’s gambit worked. No one who read the opening could put the novel down. All it needed was a grabby title. Benchley had spent months kicking around potential names (“Dark White”? “The Edge of Gloom”?). Finally, just hours before deadline, he found it.

“Jaws,” he wrote on the manuscript’s cover page.

When it was released in early 1974, Benchley’s novel kicked off a feeding frenzy in the publishing industry — and in Hollywood. “Jaws” spent months on the bestseller lists, turned Benchley from an unknown to a literary celebrity and, of course, became the basis for Steven Spielberg’s blockbuster 1975 film adaptation.

While most readers were drawn to the book’s shark-centric storyline, “Jaws” rode multiple mid- 1970s cultural waves: It was also a novel about a frayed marriage, a financially iffy town and a corrupt local government — released at a time of skyrocketing divorce rates, mass unemployment and a presidential scandal. At a time of change and uncertainty, “Jaws” functioned as an allegory for whatever scared or angered the reader.

The success of “Jaws” — at bookstores and in theaters — had unforeseen consequences for Benchley. Throughout the late ’70s, he watched in frustration as sharks were branded public enemies. Benchley, a longtime sea lover, spent decades transforming himself into an amicable shark defender, reminding readers that the man-eater in “Jaws” was a work of fiction.

“Many people took ‘Jaws’ as a license to go out and kill sharks,” said Wendy Benchley, who was married to Benchley from 1964 until his death in 2006. “We tried to use ‘Jaws’ in every way we could to sound the alarm about sharks and about how important they were to the ecosystem.”

It was an unlikely legacy for Benchley’s gruesome, toothsome book — one the author never expected to be a hit in the first place. He didn’t think readers would seize on a beast-versus-beach tale from a first-time novelist. And the idea of “Jaws,” with its monster shark, making it to the big screen seemed unworkable to him.

“Everything about it was an accident,” Benchley would say decades after the summer of “Jaws” — the book, the phenomenon, the whole thing.

Benchley was just starting his writing career when, in 1964, he spotted a newspaper story about a fisherman named Frank Mundus, who’d used harpoons to capture a giant great white shark off Montauk Point.

Benchley clipped the article from The New York Daily News and put it in his wallet, where it would stay for the next several years. During that time, Benchley worked as an editor at Newsweek and later as a speechwriter for Lyndon B. Johnson. When his White House gig ended in 1969, Benchley began freelancing for numerous publications — writing book reviews, film reviews and occasional travel pieces.

But Benchley hadn’t forgotten about that oversized shark at Long Island. Benchley’s first stab at “Jaws” was rejected by Congdon, who thought the book was trying too hard to be humorous. But by the second draft, parts of it were coming together — especially that first chapter, in which the shark glides through the night water, “propelled by short sweeps of its crescent tail.”

Kate Medina was an editorial assistant at Doubleday in the early ’70s when she was recruited to help guide Benchley through the revision process. “I don’t think the beginning of ‘Jaws’ was ever changed,” she recalled.

“Peter had from the start a strong and intuitive sense of pace and of storytelling, and a deep love for writing and for the sea,” Medina, now an executive editorial director at Random House, wrote in an email. “Every time that fish swam into the book, it was great.”

With Medina’s assistance, Benchley developed the novel’s many nonaquatic characters, including its three unlikely heroes: Martin Brody, the harried police chief of the fictitious town of Amity, Long Island; Matt Hooper, an oceanographer brought in to track the shark; and Quint, a rugged fisherman tasked with killing the fish.

Those who are familiar with only the big-screen version of “Jaws” may be surprised by the many juicy subplots in Benchley’s novel. Amity itself is on the brink of ruin, having barely survived the early ’70s recession. Also in decline: Brody’s marriage to his class-conscious wife, Ellen, who has a sexually charged encounter with Hooper at a surf-and-turf spot. Then there’s the town’s mayor, Larry Vaughn, who’s so deeply indebted to the mob, he’ll do whatever it takes to keep the beaches open — even if it means people die.

For all the intrigue, though, the book’s main attraction is the shark lurking in the background, its actions and desires described with clinical rigor.

In February 1974, “Jaws” hit bookstores. The cover image was striking: a minimalist illustration of an open-mouthed shark racing toward a hapless female swimmer.

As the summer drew near, “Jaws” became an essential beach read — albeit one best experienced far from the shoreline. And its popularity ballooned even more after the film adaptation — which was co-written by Benchley and Carl Gottlieb and featured a famously temperamental mechanical shark — came out in 1975.

Not long before his death in 2006, Benchley looked back on “Jaws” with what sounded like a tinge of regret. “Knowing what I know now,” he said, “I could never write that book today. Sharks don’t target human beings, and they certainly don’t hold grudges.”

But Wendy Benchley said the author remained proud of “Jaws” and of its impact — not just on readers and moviegoers, but also ultimately on the awareness of sharks. “He was at peace with it,” she said.

And over the years, whenever someone brought up how much “Jaws” had scared them, he had a quick and punchy response: “It was just a novel.”