There were a few typos or just confusingly written sentences, particularly in scene and action descriptions, but occasionally in dialogue, which made me feel that the publisher was in such a hurry to make this book hit the shelves that they didn't edit it as much as it deserved.
I have trouble reading time travel books. Ever since I read the Gideon Trilogy by Linda Buckley-Archer, the only kind of time travel stories I've been able to read without having trouble suspending my imagination are stories where people go back and everything they do already happened. In Harry Potter and the Prisoner of Azkaban Rowling used the second (and more believable in my opinion) method of time travel. In this one she used the first. I didn't have nearly as much trouble suspending my imagination for this book as I usually do with this type of book, which is probably because, even when she's writing stories as a play instead of a novel, Rowling is still very good with words. I was still skeptical at a few parts though. For instance, after Albus and Scorpius messed up time for the first time, Harry acted really weird, strict and even mean. This felt out of character for Harry, but I blamed it on the time warp that had messed up Ron and Hermione's relationship, but then after the reparation of time, Draco, Ginny and the other characters referred to Harry's forbidding Albus to be friends with Scorpius, and Draco and Harry's duel, which means that the Harry's actions happened in both the time warp and the unaltered time, which, in turn means that Harry acted really bizarrely out of character no matter which version of time you're looking at.
I was so nervous reading this book. Nearly everything Albus Severus did made me say "poor Harry..." After all, J.K. Rowling said that if she could say anything to Harry she'd apologize for all she put him through, and now she put him through the pain of a child who doesn't appear to like him. I had a little bit of trouble with Cedric's character. After my Pottermore sorting I was told that there were almost no Hufflepuffs who fell into dark magic so I found it saddening to learn that humiliation could lead Cedric to become a Death Eater.
In some ways I felt like all of Hermione and Ron's interactions were an apology for telling us that those two probably shouldn't have ended up together. In some ways I don't mind because I really like Ron and Hermione together, but there were also times where it felt a little bit forced.
I have one other problem with the book. Overall the messages were, as with the other Harry Potter books, good. Be kind. Be brave. Be careful and don't mess with time because the smallest actions can change major things in the future (so be kind and careful even if you aren't hanging out in the past as you don't know how your actions may affect the world.) But there was one message I saw that struck me as bad, and that was that you are what your parents are. This message is not a dominating force and the fact that Albus, Harry Potter's son, is kind of a jerk and Scorpius, Draco's son is very kind (and my favorite new character in the series.) But Rose Granger-Weasley has Hermione's smarts, but both Ron and Hermione's judgemental attitude and some of the snobbishness that Hermione showed when she was on the Hogwart's Express for the first time. Worse, Dephi was Tom Marvolo Riddle's daughter, and she was evil, warped and willing to destroy anything in her way. I'm sure no one is surprised that she is also Bellatrix's daughter, but I really would have liked to see a descendant of Voldemort who was kind and considerate and trying to be the exact opposite of her (or his if the descendant had been a he) parents, and what we got instead was a woman who was more than willing to follow her parents in every way. Obviously upbringing can affect a person very much and it does sound like Dephi was raised by a Death Eater who would have brought her up to love and admire the parents who didn't deserve either emotion, but again, I really would have liked to see a child of Voldemort who was the exact opposite of her parents.
Even though I have discussed more things that I had a problem with than things that I liked about this book, overall I still thought it was a good Harry Potter book. Was it up to par with the original series? Not quite, but I still did enjoy it. I loved Scorpius and enjoyed seeing what Harry, Ron, Hermione, Ginny and Draco were up to, and how their kids were faring. I also really liked seeing how much more Snape's character (would have) developed (if he had survived) in the second time warp. The book had plenty of places where I laughed out loud, just like the original books, and it also had quite a few places where I was going "awwwww."
I do suggest this book to Potter fans, but don't expect it to be quite as good as the original series.