This play is literally fan fiction and you cannot convince me otherwise. As a hardcore Harry Potter fan I have enjoyed reading this very much, although at least 80% of this are storylines I've read before on the internet. 
 I can perfectly imagine this as a play and I am sure they have done a magnificent work with stage presentation, design and props. However, it falls short as a book. There's not quite enough plot for an actual novel and I guess it's not what it's aiming for - still feels a lil bit disappointing though. 
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 My favorite thing: Scorpius is a beautiful cinnamon roll and I love him. 
 My least favorite: Ron became a walking joke. (I can picture how this character works in a play but it doesn't make it less annoying to read). 
 Objectively the worst: Delphi/Augurey, aka Worst-plot-device-ever. 
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