Harry Potter And The Cursed Child: 7 Ups & 3 Downs
2. Some Meddling With Mythology
Inevitably, complaints have already been raised about the changes to the mythology in the Cursed Child. The story wasn't written by Rowling, and although she did oversee it (and you'd assume have a fair bit of creative control), it would seem that mistakes have slipped in that do jar with what we know of the original series.
The one dominating most of the headlines, and garnering the most complaints, is the use of time-travel. It's not just the time-turners are back in play, despite supposedly being destroyed in Battle of the Department of Mysteries, but the way time-travel works: the newfangled time-turners allow users to go back decades, creating a butterfly effect and alternate timelines. It goes against various, vaguely established rules of time-travel within this universe - which Rowling tried to expand upon via Pottermore, stating you could go back five hours from the future without causing serious damage, but here's it's five minutes in the past, but however far back you like.
There are a few other inconsistencies sure to be niggling away at fans as well. The Polyjuice Potion, for example, is apparently remarkably easy to make now, a far cry from the days of Hermione and co sneaking around and toiling away at it. Ron is closer to being like one of the twins, though that's perhaps to do with his role at the joke shop (and his love for Hermione still shines through). Harry, a Ministry official, interferes at Hogwarts, something Dumbledore was always against.
I don't think they particularly ruin the story, but it's strange to see little errors creep in when Rowling had previously taken so much care in the creation of this world, but perhaps that's because it's not directly from her own quill.