Manhattan Beach is not the novel Jennifer Egan set out to write, in large part because Jennifer Egan, Pulitzer Prize winner, doesn’t write by following plans. “I don’t really know what I’m going to do before I do it,” she tells me over salads—she recommends the arugula, “if you’re in a salad-y mood, it’s very salad-y”—at Olea in her neighborhood of Fort Greene, Brooklyn, which, coincidentally, is about a mile from the Brooklyn Navy Yard, where much of the World War II–era novel takes place.

Not that she necessarily knew that, either, starting out. In 2004—after Look at Me, an ambitious and aggressively sharp (and eerily prescient) narrative tangle; before the publication of her techno-Gothic metathriller The Keep—Egan had a fellowship at the New York Public Library to write a novel of some kind (what kind she isn’t sure—“it’d be funny to look back at that proposal”). What she did know is that she was interested in New York City circa WWII. “I think it went back to 9/11,” she says. “I was interested in America as a superpower, and it felt to me like, in some way, that was ending or changing with 9/11. That led me to think about when it had begun and how, which was the second world war.”

If you are following the timeline here: she did not write Manhattan Beach at the library. (What she actually did was finish The Keep. “I had just had my second kid, and I was way behind.”) But the fellowship required a presentation, which required she do something with this war idea, which led her on a deep dive into the maritime history of the city. Now, it’s easy to forget the waterways altogether, unless you’re a broker or an urban planner or a homeowner calculating flood insurance rates. “But then,” Egan says, “the entire orientation of the city was out toward the water.” And if you’re “even thinking vaguely about the New York waterfront during the war,” you end up at the Navy Yard. Which is where, she imagined, her novel would start.

It does not spoil much to say the novel does not open with a woman in the Navy Yard working on ships. The novel, instead, opens on the eponymous beach—a beach Egan had never visited and didn’t know she was writing about until she wrote it—with three figures: Anna Kerrigan, nearly 12 years old; her doting father, Eddie, a runner for a crooked union don; and a family-oriented gangster named Dexter Styles, who, much like the beach, had not occurred to Egan before she wrote him. It was also immediately clear to Egan that Anna had a sister, but the sister wasn’t there. “I didn’t know why. I thought, Who is she? Why is she not there? Then they go home, and there she is. That’s really how it came to me,” Egan says. Lydia, we learn—we all learn, Egan included—is severely disabled, unable to walk or speak, conscious of everything. To hear her tell it, Lydia was less a creation than a discovery: a virgin birth, like the beach. “It’s a mysterious process, you know,” reflects Egan. “It’s like dreaming. It is dreaming.”

Soon, though, we do get to the woman at the Navy Yard: Anna is 19, mind-numbingly employed inspecting battleship parts, longing to join the ranks of the yard’scivilian divers, repairing ships, clearing salvage. No woman at the yard has ever done it, but Anna is determined. Eddie, by now, has been gone five years.

Manhattan Beach is Egan’s most novel-y novel yet (if you’re in the mood for a novel, it’s very novel-y). “After stretching the boundaries of fiction in myriad ways,” our reviewer writes—novels in stories, stories in tweets—she does “perhaps the only thing left that could surprise: she writes a thoroughly traditional novel.” But while she’s quick to agree that it is more conventional than her previous work, it was hardly intentional. “It sort of feels like an accident that it ended up being that way,” she says. “I thought it would be very narratively flexible and innovative, or I hoped so.” Egan laughs: “I guess the minute you start hoping you'll be innovative, it’s a sign that you need to get back to basics.” Initially, she thought 9/11 might play a direct role, that she might leap forward in time, like in A Visit from the Goon Squad(2010). “It fell so flat,” she recalls. Because, here’s the thing, Egan tells me: “radical structural notions do not work if there’s another way to tell the story.” And this time, for the first time, maybe, there was.

“In a way, I just wanted to write a kind of old-fashioned adventure story,” Egan says. “I really wanted a lot of big events. And I love that it has that stuff—I want to write more books like that, not just about people and their emotions and their problems but, like, shipwrecks, adventures, murders.” (Manhattan Beach has all three.)

But writing grand historical fiction came with a whole suite of new challenges. By the time she started actually writing, the project had been simmering for eight years, and while there were certain things she knew she wanted to happen in the book, the diving among them, she couldn’t figure out “how to make them happen credibly,” and—moreover—she couldn’t really figure out why she was trying so hard to make them happen at all. And all of it seemed to require infinite technical knowledge she still didn’t have: about diving, about the merchant marines, about gangsters.

She almost abandoned the book after the first draft, a year and a half writing longhand. “I typed it up and I read it”—this is her standard process and “often a low point”—but this was “even worse.” And Egan might have ditched the whole thing, “no regrets, no harm, no foul,” except that she wasn’t sure what else she’d do. “Honestly, I just thought, ‘OK, fine, you’re not going to do this. What are you going to do? You can’t just do nothing.’ ” But what she wanted to do was to keep researching. “And I thought, ‘If I feel that way, it’s a sign that I am going to write this book, because there's no other reason for me to want to know these things, or for them to feel so vital.’ ”

For all its big events, the greatest surprise—to Egan more than anyone—is how deeply personal the book is: it is about the Brooklyn waterfront, like she intended, about Americanness, about women and power; none of that was unexpected. But there is something else. “To me, the book is so clearly about the complicated task for a parent of accepting that his or her child will be his or her own person. To me, that’s really what the book is about—how hard that is to do and how wrenching it can be. That’s really why Eddie leaves, in my mind. He can’t bear it.” It hits close: Egan’s sons, elementary schoolers when she wrote Goon Squad, are now in their teens.

“Luckily, I didn’t put all this together, because if I had, I would have felt like, Oh my God, I can’t work on this, it’s too much like my life!” says Egan. But the setting was so different, so distant, she didn’t see it until it was done. It’s about Americanness and women and power and gangsters and boats and 9/11, but “it’s really about parenthood,” Egan says. “God, I never thought I would write a book about that. I hope I disguised it well.”

Rachel Sugar is a writer living in New York.