I wasn't expecting much, so I wasn't really disappointed. The story itself was interesting in places, but basically flawed, and not very well written. Wooden lines such as "I can give you Professor Longbottom - his knowledge of plants may prove useful" are ubiquitous, and often give the impression you are immersed in one of the farcical RPG's from 10 years ago. 
 However, I'm sure the play itself will be well produced and enjoyable, especially for families. Indeed, I expect the pedestrian quality of the script would have been far better disguised if it hadn't been released in print. A fully thought-through prose version of the story might even have been passably good. 
 I'm still certain there are plenty of good stories which could emerge from the Harry Potter universe, but this one was quite bad. 
 JM 19/08/16