LONDON — There are fans with wands and wizard costumes, midnight book parties and throngs of excited muggles. Harry Potter’s magic is back.

Nine years after J.K. Rowling’s final novel about the boy wizard, Harry has returned, on the stage and the page – and he’s still producing commercial alchemy.

“Harry Potter and the Cursed Child ,” a two-part stage drama that picks up 19 years after the novels ended, has its gala opening Saturday at London’s Palace Theatre. It’s already a hit. Although producers won’t release ticket sales figures, the show is largely sold out through December 2017; another 250,000 tickets will go on sale Aug. 4.

“It is event theater in the truest sense,” said theater commentator Terri Paddock, who co-founded stage website MyTheatreMates. “You can’t turn up at the Palace Theatre and not get caught up in the excitement. There is such a buzz: passers-by stopping and staring … children with their capes and wands and wizard excitement.”

It is not just the theater that is seeing a Potter-related boom. Booksellers expect a bonanza when the script is published Sunday.