In 2007, during the last round of Potter-mania, shoppers check out their new copies of “Harry Potter and the Deathly Hallows” at the Changing Hands Bookstore in Tempe, Ariz. (Ross D. Franklin/AP)

On Saturday night, bookstores across the country will do something they haven’t done in a long while: Fling open their doors to host late-night parties for masses of Muggles looking to get their Harry Potter fix.

The last time booksellers were revving the hype machine for a new title in J.K. Rowling’s wizarding series, the year was 2007. Borders still existed. So did Waldenbooks and B. Dalton. Amazon was months from releasing the first Kindle e-reader.

Now, even as the business has changed dramatically, the splashy sales expectations for Harry and friends have not: Barnes & Noble and Amazon each say that “Harry Potter and the Cursed Child” is their most pre-ordered book since the last Potter installment, and Barnes & Noble projects that  it will be the chain’s biggest-selling title of the year. Scholastic, the book’s publisher in the U.S. market, is expecting double-digit growth in its trade-publishing division in the next year thanks in large part to an anticipated Potter frenzy.

And so retailers big and small are dusting off the sorting hats and the quidditch brooms this weekend, testing whether the old formula of costume competitions, trivia battles and games like “pin the nose on Voldemort” can still work in a new shopping moment, one in which even more sales have moved online and when the original cohort of kiddie Potter fans has grown up.

[A roundup of D.C.-area ‘Harry Potter’ release parties]

At Barnes & Noble, executives plan to lean into the idea that the Harry Potter fan base is perhaps more multi-generational than it was the last time around, since the original millennial Potter readers are now in their 20s.

Back in 2007, the sweet spot of our events was really focused on the 8-to-10-year-old,” said Mary Amicucci, chief merchandising officer at Barnes & Noble. “Now we’re going to have something of readers of all ages.”

For example, during the launch parties, instead of just doing kid-friendly craft activities such as wand-making, Barnes & Noble will be tricking out its stores with a Muggle Wall where longtime readers can scrawl their favorite memories of the series. (“Muggles” is the Potter-world term for us ordinary humans who don’t have magical powers.)

There’s plenty of reason beyond the strong preorder numbers to believe that Barnes & Noble and other retailers will have a hit on their hands with “The Cursed Child”: Harry Potter has remained close to the pop culture epicenter thanks to hit movie versions of the books and the debut of the Wizarding World of Harry Potter theme parks at Universal Studios.

And yet it remains to be seen how Potter loyalists will react to the format of this book, which does not fit the mold of the first seven stories. “The Cursed Child” is written as a play, one that is set to debut onstage this weekend at London’s Palace Theatre. The script is written by Jack Thorne and is based on an original story he developed with Rowling and John Tiffany, though Rowling’s byline gets top billing on the book. And while the rest of the Potter series followed Harry, Hermione and company through their adolescent years at Hogwarts, “The Cursed Child” is set many years down the road, featuring the original characters as grown-ups sending their own children off to magic school.

Ron Charles previews the play "Harry Potter and the Cursed Child" by Jack Thorn and based off of a story by J.K. Rowling. (Ron Charles/The Washington Post)

[Want to see ‘Harry Potter’ onstage? Good luck!]

Scholastic has printed 4.5 million copies of the book for the North American market this time around, fewer than it printed for the first run of “Harry Potter and the Deathly Hallows.” But Ellie Berger, president of trade publishing at Scholastic, said this simply reflects a compressed timeline the publisher faced in getting the final version of the script.

Despite the different story structure, Berger said, “It’s the characters we know, who we love. There’s a lot of familiar things in this new story. Whatever the format, there’s new content, there’s new adventure.” 

And yet Steven Aarons, owner of independent toy and book store Child’s Play, said he’s expecting that his sales of “The Cursed Child” might reach only 30 to 50 percent of what they did for “Deathly Hallows.” He’s not sure the theatrical play format will have quite the same appeal, and fans are no longer used to the ritual of coming out for a new Harry Potter title roughly every year.

And yet at his four locations in the Washington region, he still expects it will be one of the most popular titles of the year, and so he’s pulling out all the stops. His McLean, Va., and Washington stores are hosting quidditch games in their parking lots Saturday night, and his Arlington location will be visited by a live owl. He said events like this are an important way to connect with the neighborhood — a crucial piece of his strategy for thriving as a small bookseller.

[It’s time for J.K. Rowling to let other people write ‘Harry Potter’ books]

Mom-and-pop bookstores like Child’s Play generally are in a different place than they were at the time of the last Potter release, said Oren Teicher, chief executive of the American Booksellers Association. In 2007, independent bookstores were often closing their doors or seeing their sales sink while Barnes & Noble was barreling ahead with plans to open 31 stores in a year.  But last year, sales at independent book shops rose 10 percent. The ABA, a trade organization for independent sellers, has seen its membership grow in each of the last seven years.

“We’ve had a modest resurgence,” Teicher said. 

Teicher said independent booksellers have benefited mightily from a broader movement by consumers toward a boutique-like shopping experience with local flavor. Consumers are often seeking small-batch, exclusive products, and even huge chains are trying to court them now with stores that have a more localized feel.

A preview performance of J.K. Rowling's new play, 'Harry Potter and the Cursed Child', earns rave reviews from the audience. (Reuters)

Another source of fresh confidence for traditional booksellers has been the slowdown in e-books, a format that was once predicted to be the final nail in the coffin for bookstores. According to data from the American Association of Publishers, sales of e-books were down 24.9 percent last year to $99.9 million. In other words, the latest selling pattern suggests that e-books aren’t going to completely subsume physical books, but that the formats will coexist — at least for a while.

And yet traditional booksellers have hardly ridden out the wave of disruption. Consider how Amazon, for example, is selling the latest Potter book. In markets where its Prime Now service is available, Prime members can get the book delivered to them between midnight and 2 a.m.  (Jeffrey P. Bezos, the chief executive of Amazon, owns The Washington Post.) In other words, after years of hammering legacy booksellers on price and selection, Amazon is continuing to find new ways to raise the competitive stakes.