It takes only a day to finish the book. Full of flaws, overall. Time travel things are easily turn out to a disaster for a story. And this' seem happened to be that way and couldnt be covered by the too obvious plot device. 
 BUT surprisingly, this thing is still enjoyable for me. Blame my poor addiction for Harry Potter series and cute boy like Scorpius Malfoy. #facepalm #facered 
 Anyway. I'd like to see the play myself.... someday.