No-spoilers alert: J.K. Rowling, your secrets are safe here. Harry Potter and the Cursed Child, the two-part sequel that starts 19 years after the final chapter in the franchise finale Harry Potter and the Deathly Hallows, began two months of sold-out previews Tuesday night at London’s Palace Theatre before its July 30th opening. In a video message released Monday, Rowling implored theatergoers to keep the play’s secrets: “Let audiences enjoy Cursed Child with all the surprises that we’ve built into the story.”

Whether the media will follow suit is another matter. Several newspapers broke with tradition and protocol last year by sending critics to the first previews of Benedict Cumberbatch’s performance in the title role of Hamlet. Interest in the stage debut of Harry Potter, in a new storyline, is no less intense: When tickets went on sale last October, 175,000 sold out in 24 hours, with fans queuing online for several hours to secure their spots. Will everyone really #KeepTheSecrets, as a golden hashtag on the souvenir tickets beseeches? So far, early verdicts from The Telegraph and the Daily Mirror were careful to stick to description rather than opinion, keeping plot details confined to the previously-announced hints the production had approved. Though there was a bit more detail in the New York Times précis.

The tricks rarely feel like tricks; that they’re happening live makes the magic often more impressive than the CG wizardry of the movies.

So suffice it to say on first viewing that John Tiffany’s staging of Jack Thorne’s play (Rowling conjured the story in concert with Thorne and Tiffany) goes to great lengths to deliver the Wizarding World without shying away from its magic. Designer Christine Jones’ (Old  Times, Hands on a Hardbody) set conjures King’s Cross and the many rooms of Hogwarts, turning on a dime. And a wide variety of ingenious stage trickery illuminates the tale, which picks things up where they were left in Rowling’s Harry Potter and the Deathly Hallows epilogue. Those tricks are often simple and age-old—like stagehands in shadows, clever light projection and pyrotechnic flashes. But the particular alchemy employed here is like nothing the West End has ever seen, and there are many ‘wow’ moments for even the greatest skeptics.

Crucially, the tricks rarely feel like tricks; that they’re happening live makes the magic often more impressive than the CG wizardry of the movies. And a score of rearranged instrumental Imogen Heap tracks might be a 180-degree shift from John Williams’ familiar theme, but it struck as no less magical.

After a thunderous round of applause when the lights went down, the 1,400-strong audience responded emphatically to plot twists, stage magic and the appearance of a live owl with oohs, ahhs and general enthusiasm. It felt more Broadway than West End (where even die-hard Cumberbatch fans saved their appreciation for the Hamlet curtain call), but this show can expect friendly audiences for many months to come on brand value alone, and it’s hard not to get into the spirit.

Harry Potter and the Cursed Child

It didn’t seem to take the fan-heavy audience any time at all to adjust to a new, older trio playing Harry, Ron and Hermione, with Jamie Parker, Paul Thornley and Noma Dumezweni in the respective roles. But the importance of the younger characters—particularly Harry Potter’s son Albus (Sam Clemmett) and Draco Malfoy’s son Scorpius (Anthony Boyle)—can’t be overstated. There was some debate in the stairwells afterwards about the identity of the Cursed Child of the title, along with anticipation that all would be revealed at Thursday night’s second part. The feeling of excitement and of being on an extended theatrical journey not available either from the books or the films recalled that of the Royal Shakespeare Company’s groundbreaking two-parter The Life and Adventures of Nicholas Nickleby more then three decades ago. This is the most significant Potter work since that last book, and the play’s script won’t be published until July 31, though it’s already topping bestseller lists.

It remains to be seen how long London’s critics will wait before weighing in on what undoubtedly will be a social-media tidal wave of discussion about the show’s merits, with plenty advice for producers Sonia Friedman and Colin Callender as they move forward toward opening and, presumably, Broadway. Matt Wolff of the International New York Times expected tonight’s preview would feature its share of media, but that full reviews would not be forthcoming. The lengthy preview, he told Deadline, is to be expected of a two-part play with staging as complex as any musical. “I’m guessing the preview period will be respected when it comes to actual, full-fledged reviews,” he said. “Hamlet was slightly different in some people’s minds in that Shakespeare’s play, of course, is a fully formed entity. This is a brand-new, two-part play that has never been staged anywhere before.”

No one in the audience found cause to balk at the 2hr45 runtime—the pace ensures it just zips by, with a story as dense as any of the books. And as the play ended—no shock to say, on a cliffhanger—anticipation for where the tale would turn in the 2h35 second part suggested no one was ready for it to end. A standing ovation was all but guaranteed, but it was brief: there was no curtain call from the cast. That will come, no doubt, with Part 2 on Thursday evening. We’ll let you know.