LONDON — In King’s Cross railway station, at the approximate location of Platform 9¾ , there bustles a small commercial temple of the multibillion-dollar Harry Potter kingdom. Within the well-stocked walls of the Harry Potter Shop, you can conduct a merchandise sweep the likes of which might cause even He-Who-Must-Not-Be-Named to collapse in swooning contemplation of licensing checks yet to be cashed.

 Wizard chess sets, Gryffindor hoodies, book bags in Slytherin green and Hufflepuff yellow, scarves, wands, Dobby dolls and Hedwig keychains. For £9.50 (about $13) you can have your photo taken with the added caption, “Have You Seen This Wizard?” For £15 ($21) they’ll create a personalized acceptance letter to Hogwarts for you. At 11 a.m. on a recent Friday, the line for a chance to pose under the Platform 9¾ sign — the magical spot where Hogwarts-bound students pass through solid brick to board the school train — was 40 tourists deep.

Want to see ‘Harry Potter’ on stage? Back of the queue, mate!

It’s breathtaking, really, the array of items and the scale of the mercantile imagination — including, of course, the Harry Potter theme parks, the Lego sets, the video games — unleashed by J.K. Rowling’s seven Potter books and eight motion pictures. Estimates of the value of the enterprise range up to an astonishing $25 billion. And now, yet another Potter bauble is being peddled, one that is a lot more expensive than those that fill the shelves at King’s Cross. This would be the stage production that began running  this week at the massively overhauled Lyric Theatre in Times Square in New York: “Harry Potter and the Cursed Child,” a two-part, 5½ -hour stage sequel to the mega-popular Potter franchise. 

The double bill has been playing to sold-out houses in London’s West End for nearly two years, and now the Broadway incarnation, which features seven actors from the London original — including those who portray grown-up Harry Potter (Jamie Parker) and Hermione Granger (Noma Dumezweni) — is pretty much guaranteed to be a long-term tenant for the Lyric. As of early March, premium tickets (on sale already through March 10, 2019) could be found on the Ticketmaster website. Two seats in Row D in the orchestra for each of the play’s two parts in late March could be yours for a total of $1,217.50, including $58 in so-called service fees; on the scalping (or resale) websites, tickets are being hawked for between $300 and $1,000 apiece.

This is all good for the theater, is it not? A pair of shows with a certified fan base, a smash hit before its final dress rehearsal, a fantastic draw for families with a desire for comfort-food entertainment?

Well, maybe.

In London, Harry Potter embraces his loyal fans

“Harry Potter and the Cursed Child” is a boon to Broadway in the sense that it bolsters a burgeoning entertainment business model, one that more than anything appreciates a sure thing, whether that is the musical stage version of “Aladdin’’ or “Frozen,” Bette Midler in a revival of “Hello, Dolly!” or Bruce Springsteen in an intimate concert. The production solves a real estate problem: what to do with a barn of a theater first refurbished in 1998 as the Ford Center for the Performing Arts (and later, the Foxwoods) that has proved difficult to fill successfully. (Both the original version of the musical “Ragtime” and the disastrous “Spider Man: Turn Off the Dark” sputtered to a close there.) And it nourishes a market that is ever more dependent on tourists, who now buy two out of every three Broadway tickets.

Still, despite the prizes the production has won and the critical plaudits it has received, the plays that have been concocted for the stage by Rowling; the show’s director, John Tiffany; and playwright Jack Thorne are more commerce than art.

There’s nothing wrong with making money, nor with assigning a project of this magnitude to Tiffany and his longtime creative partner, choreographer Steven Hoggett, who together staged impressive works such as “Black Watch” and the revival of “The Glass Menagerie” with Cherry Jones. But let’s not bow too deeply before the altar of the Boy Who Lived. I can’t help feeling that it’s a bit of a cheat to conquer Broadway on the reputation of such an international juggernaut, one that is so calculated to capi­tal­ize on past triumphs that it has sucked a lot of the air out of the current Broadway season. Convinced that “Harry Potter” would dominate the play categories at this June’s Tony Awards, for instance, some other producers were reluctant to bring in works to compete with the Potter plays; no other new play, in fact, is opening on Broadway this spring, only play revivals, at both commercial and nonprofit playhouses. 

Which means that the only new plays on Broadway over the next several months are tailored for the same audience that goes to New York for family musicals, like such soon-to-open properties as Disney’s “Frozen” or perhaps the Jimmy Buffett show, “Escape to Margaritaville.” As a result, the idea of Broadway as a destination for the serious, adult theatergoer grows a shade dimmer.

“Harry Potter and the Cursed Child” is less a dramatic investigation than a live dive into the fantasy genre. It’s two evenings of what you might term spectacular fan fiction. I saw the plays in London late in 2016, and although the designers display heroic levels of invention — people such as Jamie Harrison, who is credited with the illusions and magic, and set and lighting designers Christine Jones and Neil Austin — this stage addition to the Potter canon has been developed with the die-hard devotee in mind. Will many people who are not already steeped in Potter lore, who cannot divine the difference between a Quidditch match and a Tri-Wizard Tournament, be held for nearly six hours of a heavily nostalgic brand of exposition? In London’s Palace Theatre, I watched my wife, who barely paid attention to my daughter and me over the years when we ruminated over the death of Sirius Black or tested each other’s knowledge of patronus charms, struggle to engage with a parade of familiar characters (and a few new ones) during the two-part drama.

Granted, in making Hogwarts kids fly on brooms, or simulating the turning back of clocks through a device Rowling and company call the Time Turner, the plays accomplish the delightful feat of revealing the clever ways the stage can compete with cinematic effects. Or rather, not so much vie, as develop its own magical language. 

The real achievement on these evenings, though, is of a strictly technical nature, and, in the cascade of super-short scenes — some running as little as a page or two of dialogue in the best-selling “special rehearsal edition script” that was sold before the plays opened — a kind of retrospective of the joys of the novels. There’s a new story, which I won’t get into here, but it really doesn’t take us anywhere new. Potter enthusiasts, of course, won’t mind; many come to immerse themselves in what they already know so well. Not for nothing do memorable figures such as Dumbledore and Umbridge and Hagrid make cameo appearances.

Harry and Hermione and Ron will find a welcome home on the new Broadway, and the plays in the Lyric will keep the Potter machine minting money. As to whether these franchise-extensions-as-theater are a healthy development for the world of the stage, count me among the unconvinced.

Harry Potter and the Cursed Child, by J.K. Rowling, John Tiffany and Jack Thorne. Directed by Tiffany, with movement by Steven Hoggett. $20-$289. At Lyric Theatre, 214 W. 43rd St., New York. Visit harrypotter.ticketmaster.com.