Among the most popular and bestselling genres over the past year and a half has been romantic fiction. For book lovers, it’s not hard to figure out why. Similar to another top-selling fiction genre during the pandemic—mysteries and thrillers—romances follow familiar (if not predictable) structures and employ routine tropes. Both genres also have signature but reliable endings: Murder mysteries almost always reveal the culprit and (oftentimes) dole out a bit of justice, while romances traditionally result in a “happily ever after.”

In other words, the predictability of these novels makes for literary comfort food, one that many readers craved in abundance during some very turbulent times.

“From talking to readers and fellow booksellers, I believe that romance has experienced a rise in readership during the last year and a half because people needed escapism and the guarantee of a happy ending, a story where, no matter the obstacles, they could be safe in the knowledge that everything was going to work out in the end,” says Billie Bloebaum of Third Street Books in McMinnville, Ore.

Romance has rules, notes Kelly Justice, owner of Fountain Bookstore in Richmond. You can bend those rules, but if you don’t have a happy ending (or a “happy for now”) it’s not a romance, she underscores.

“The sheer massive quantity of romance and the emergence of a wider array of voices and representations has meant that we have a romance where almost any reader can see themselves,” Justice says. “And that trend is only expanding. And let’s be honest: It’s fun! What was fun about the last two years? Not much. Even as (or if) things improve, who doesn’t want fun? People came to try a new escape and stayed for the good times and the great community.”

Just take a cursory glance at the current lineup on the New York Times’ Best Sellers lists for fiction—especially paperback trade fiction—and you’ll see romance novels flooding the lists, from Christina Lauren’s The Unhoneymooners (first published in 2019 but has seen an uptick in sales amid news of a Hollywood adaptation) to one of this summer’s hottest hits, Emily Henry’s People We Meet on Vacation.

Unit sales for romance books topped 47 million in the 12 months ending March 2021 (including print and e-book sales combined), representing an increase of 24% from the previous year, according to NPD BookScan. Romance accounted for 18% of adult fiction unit sales in the 12 months ending March 2021, making it the second most popular fiction genre overall—second only to general adult fiction—which accounted for 30% of adult fiction sales in the same time frame.

A number of booksellers—digital and brick-and-mortar alike—are making the the most of the genre’s attraction. On Saturday, Aug. 21, online retailer Bookshop.org is partnering with Bookstore Romance Day, back this year for a third time to celebrate a genre that has often been dismissed by readers and critics.

“I think this very guarantee of a ‘happily ever after’ is part of what has contributed to romance being less respected. It has been viewed as light or fluffy or frivolous,” says Bloebaum, who is also the founder of Bookstore Romance Day. “I hope that the increased interest of the last year continues and that attitudes toward the genre continue to change as well.”

“Romance readers are particularly voracious, and as passionate as the novels they read,” Nadine Vassallo, director of operations at Bookshop.org, tells Fortune. “We love connecting romance fans with handpicked recommendations from equally ardent indie booksellers. Romance readers and booksellers are essential to the book industry at large and to the Bookshop.org community.”

Over 250 bookstores have signed up to participate this year, with dozens of virtual events with famous authors, curated reading lists, exclusive giveaways, and the Discover New Romance Award, which names the best in unpublished and self-published romance, as determined by a panel of independent booksellers.

“This year’s Bookstore Romance Day is maybe the most important one since we started,” Bloebaum says. “While romance readership has increased, a lot of independent bookstores have struggled due to not being able to have customers in the store or in-person events. Connecting those stores to romance readers both new and old has the potential to benefit both, with increased sales for the stores and a local, friendly option for both purchasing and discovery for readers.”