Okay, I actually really liked this book. It's a good read but I didn't like some parts. SPOILERS AHEAD
Harry and Ron were really out of character from the original series. Harry disrespecting McGonagall?! He would not do it even in a different life. And he also said he didn't need Dumbledore while we all (and Harry himself) know the truth. Basically, Harry and his son, Albus were acting like a**holes throughout. And Voldemort has a child?!?! And other stuff...
As for the good parts, Scorpius was a great character and such a cinnamon roll. The writing on the blanket thing was a cool idea. Liked the alternate reality plots too.
This book can be called as good if you ignore the gaping plot holes and contradictions to canon. Best read by treating it as separate from the series.