When Pamela Dorman acquired Shari Lapena’s thriller The Couple Next Door in the fall of 2015, there were strikes against the novel. While Dorman loved the book, a twisty tale about a couple whose baby goes missing from their upstate New York home, it was part of an incredibly crowded subgenre of psychological suspense novels vying to capture the readers of megahits Gone Girl and The Girl on the Train. The novel’s Canadian author was also an unknown quantity in the U.S. (where the book would serve as her debut).

Now The Couple Next Door has become a main stay on the bestseller list, having sold more than 500,000 copies across all formats. The team at Viking, where Dorman’s eponymous imprint is housed, said the novel, released in hardcover in August 2016, was helped along by the things that, in industry parlance, make up a book’s “package”—namely its title, jacket, and cover copy.

The jacket, which went through nearly 50 iterations, initially featured two people, since the book’s title refers to a couple. The final version, which shows the silhouette of a woman’s face, was a revelation, according to Viking publisher Brian Tart. “It took us a long time to get the cover right,” he said. The early versions of the jacket “didn’t signal anything” to the reader about the book, he explained, noting that they also hid the compelling title—which both he and Dorman felt was one of the novel’s strongest selling points. The chosen jacket worked so well, Tart feels, because it put the book’s title front and center. “Only after you see the title does the image come into play.”

Timing was also key. The book was fast-tracked immediately after acquisition because its category—which Tart and his colleagues call “domestic suspense”—was already, at that point in 2015, quite full. “It’s a bit of a fool’s game, trying to predict when a category will be overpublished,” Tart said, while acknowledging that Viking “didn’t want to sit on this book” out of fear that readers would be growing weary of the subgenre.

To an extent, Viking got lucky with its gamble on the staying power of domestic suspense. Despite predictions to the contrary, the category has not cooled off. (Arguably it has remained hot since late 2012, when Gone Girl started burning up the charts.) Lapena’s novel, which came out in paperback May 30 and hit #7 on PW’s paperback bestseller list for the week ended July 30, joined three other titles in the domestic suspense category in the top 12 (Ruth Ware’s The Woman in Cabin 10 at #1, B.A. Paris’s Behind Closed Doors at #5, and Megan Miranda’s All the Missing Girls at #12).

Olivia Taussig, a senior publicist at Viking, believes Lapena’s novel, like many of the other domestic suspense novels that have reached (and stayed on) the bestseller lists, hit in large part because of how it was presented to readers. “So much of the selling of these books seems to be about packaging,” she said, citing other hits by authors like Ware and Fiona Barton (whose 2016 novel The Widow was promoted as a thriller similar to The Girl on the Train and Gone Girl). Noting that Lapena didn’t receive much prepublication press, Taussig said she felt readers responded to a cover that evoked other bestsellers in the subgenre, and the fact that the book is such a satisfying read.

Viking certainly tied the promotion of The Couple Next Door to its readability, touting it as a “one-sit read” in a series of targeted print and online ads. Focusing on women 30–55, Viking did much of its print and digital outreach on the websites of Entertainment Weekly, the New Yorker, and NPR.

Later in the book’s life, Viking hit on another way to expand the novel’s readership: comparing it to the bestseller Big Little Lies. Although Liane Moriarty’s 2014 novel, about a group of secret-carrying mothers in the upscale enclave of Monterey, Calif., is not domestic suspense, much less a thriller, the book does feature a plot twist. And, as Dorman noted, it focuses on the interior lives of a group of women. Big Little Lies, which was given a new lease on the bestseller list after being adapted into an HBO miniseries that debuted in April, is something Dorman said “plays really well” to the readership for The Couple Next Door.

Viking’s marketing team used the Moriarty comparison to, as Taussig explained, help The Couple Next Door break out beyond “a traditional thriller audience.” The marketing team came up with a new tagline for the book: “It all started at a dinner party.” The line, Taussig said, was intended to feel “reminiscent of Moriarty’s book,” and was featured in a new series of ads on social media, including on Facebook, where Viking targeted Moriarty readers.

The Big Little Lies comparison, in Dorman’s view, moved Lapena’s novel toward the women’s fiction category and a wider audience. Domestic suspense, Dorman explained, is really “anything that has to do with secrets and lies in a marriage.” And this, of course, is a popular theme in women’s fiction, and fiction in general.

Ultimately, though, for Dorman the category overlaps were less important than the fundamentals: The Couple Next Door made good on its promise of being hard to put down. “What Shari can do better than anyone is plot, and I think [The Couple Next Door] would sell anytime because it really delivers.”

Lapena’s new novel, The Stranger in the House, will be published by Pamela Dorman Books on August 15, with an announced first printing of 150,000 copies.