​Can a middle-aged "Harry Potter" revive the book industry?

Harry Potter's biggest battle may not be fighting Death Eaters or soul-sucking Dementors, but using his middle-aged magic to breathe life into a struggling book industry.

The latest installment in the Harry Potter franchise, "Harry Potter and the Cursed Child," was released on Sunday and is sitting at the top of Amazon's best-seller list. Even though it's billed by publisher Scholastic as the eighth in the series, the book isn't a novel, but a script of a play that's currently playing in London. Reviews have ranged from positive, such as The New York Times' Michio Kakutani calling it "electric and nonstop," to disappointed, with The Washington Post declaring, "The magic is stunted."

The book industry is likely hoping that fans focus on the positive, given that past Harry Potter releases have been credited with lifting the overall industry because of their phenomenal sales as well as spurring kids and adults to seek out other fantasy series. The publishing industry has been struggling during the past several years, with sales declining 2.6 percent in 2015, according to the Association of American Publishers.

Whether Harry Potter, who has now entered middle age in "The Cursed Child," can still put a spell on readers may not be known for days, since publisher Scholastic (SCHL) said it won't have sales data until later this week. The initial print run was 4.5 million, which places the book in between the initial print runs for "Harry Potter and the Goblet of Fire" (3.8 million copies) and "Harry Potter and the Order of the Phoenix" (6.8 million copies.)

"The Cursed Child," at No. 1 on Amazon's best sellers list, is trailed by "Harry Potter and the Sorcerer's Stone" standing in the third slot. (A pocket edition of the U.S. Constitution is currently the second best-selling book on Amazon, following last week's widely watched DNC speech by Muslim-American lawyer Khizr Khan that challenged Donald Trump's knowledge of the document.)

Like other Potter books, "The Cursed Child" was heralded by midnight release parties at bookstores across the country, with fans crowding into stores to grab their copy when the clock struck twelve. But with almost two decades having passed since the first Harry Potter was released, it's unclear whether the same fervor still exists for the series.

Then there are the mixed reader reactions, with many early reviews on Amazon veering toward the negative. Some focus on the fact that Rowling didn't herself write the play, although it's credited as "based on an original new story by J.K. Rowling." The book is the creation of playwright Jack Thorne, who has written for TV shows including "Shameless" and "Skins."

"This cannot be over stated: this IS NOT A HARRY POTTER BOOK," one reviewer wrote on Amazon. "This is a shadow of a Harry Potter book ... it was a short predictable story missing all of the magic both literal and figurative that made you fall in love with Harry Potter."

Given that the original Harry Potter series became a cultural juggernaut based on early word of mouth recommendations from friends, such reader reviews may suggest that "The Cursed Child" won't hit upon the same success as the earlier books. Still, fans have another chance at finding the original magic when Rowling's "Fantastic Beasts and Where to Find Them: The Original Screenplay" is released in November.

After that, it might be time to say goodbye to new Harry Potter books, Rowling hinted on Saturday. Speaking about "The Cursed Child," the author told Reuters, "So, I'm thrilled to see it realized so beautifully but, no, Harry is done now."