Harry Potter and the Cursed Child theatre review: JK Rowling delivers another masterpiece

It is easy to be sceptical about how interesting life could be after the great darkness has been defeated in the battle for the future of the wizarding world. But what if happily-ever-after isn't so happy after all and can even be changed with a time-turner? With this neat idea this is the post-Voldemort (by the way, it's pronounced Vol-de-more) world we find ourselves in.

The stage production of Cursed Child picks up where we last left Harry and his scar in Deathly Hallows, replaying the final scene where Harry and Ginny send their son Albus Severus off to Hogwarts for the first time. The play proceeds in the format of a part family soap opera, part choose-your-own-adventure. It is initially fragmented as we catch up on the 19 years that have passed, and the whirring scene changes – often accompanied by unnecessary choreography – are at times hard to navigate, even for Potter devotees.

I was one of the fans who was dubious when I heard JK Rowling was writing an "eighth book" in the form of a play. Much as I longed to reopen the world of Hogwarts and Hagrid, what more was there to say? How many sequels have ended up only diminishing instead of reinforcing? I need not have worried. Of course Rowling would make it a masterpiece and of course playwright Jack Thorne and director John Tiffany would make it a spectacle.

This is a razzle-dazzle production with hugely interactive stage tricks that leave Vegas' illusionists for dead. It is a play unlike any other and is surely set to rewrite how theatre is staged in future. At times I had to remind myself I was not watching a film with CGI but a play, the magical tricks were so magnificently staged. In the opening minutes the cast change from street clothes into their robes in a seeming jump on the stage. I'm still not sure how they did it. When time is turned the stage visibly shimmers and moves bubble-like, as if entering a time warp. Dementors – ghoulish figures – fly around the theatre as they search for souls to suck the life from. After imbibing polyjuice, the younger cast morphs into the older cast right before your eyes. Even set changes are performed with a flourish as stage hands flick their capes across their props before removing them from stage.

At my showing, the audience gasped, cried, clapped, cheered and even booed the actors who played the villains at curtain call, but sometimes it felt like there were waves of complacency over the audience when they failed to notice another seemingly impossible transformation. Or it could have been the production was crammed with so many sensations it was hard to register all of them at once.

As the play slows down it crystallises around two main characters, one illegal magical (and literary) device and some central themes. Firstly, daddy issues run deep. In fact, magic seems subsidiary to the family dramas in the first half of act one. Harry might be known for his courage and bravery but as a dad he's downright crap, telling his son Albus in one heated argument that "sometimes I wish you weren't my son". Ginny Weasley, now Harry's wife, continues to play a minor role even though the family tensions set the backdrop for Cursed Child – it is somewhat of a shame but this is a play all about father and son. It's the same story over at the Malfoys, where Draco's only heir is a neurotic, quirky and utterly lovable geek who, thanks to Anthony Boyle's brilliant performance, is the star of the show.

Other notable performances include the wonderfully dynamic, bubbly and energetic Esther Smith who plays Delphi Diggory, (relative of Cedric who died in the Triwizard tournament in the book Goblet of Fire - a death that dominates the storyline of Cursed Child).

Paul Thornley shines as Ron Weasley, likewise Alex Price as Draco and Sam Clemmett as Albus. Harry's warmth and altruism is hard to find in Jamie Parker's version of Potter Snr, but granted the script has him acting like a bit of a pratt most of the time. The firm and forthright Hermione put forward by Noma Dumezweni is hard to reconcile with the Granger of the books and films – a testament more to Emma Watson's commandeering ownership of the role rather than a criticism of Dumezweni.

As you leave you are handed badges and warned to #keepthesecrets. It is a testament to muggles alike that the play, which has been in preview since June 2016, has not been spoiled or leaked. Put simply, Cursed Child is a spellbinding and magical experience that will delight, shock and move you. While you will want to keep the secrets, you will leave telling everyone you know to go and see it.

Harry Potter and the Cursed Child is showing at the Palace Theatre in London. The script will be published this weekend.