Harry Potter and the Cursed Child was written by J.K. Rowling, John Tiffany, and Jack Thorne. It is the eighth installment in the Harry Potter series. Its main characters are Albus Potter and Scorpius Malfoy. They steal a Time-Turner and go back in time to try and save Cedric Diggory (At least 4 times.), but end up with bad results (Voldemort doesn't die in the Battle of Hogwarts). They get stuck in time and Harry, Ginny, Draco, Ron, and Hermione have to go back and save them. In the end history is not altered.
I thought the book was great, even if it was a little hard to follow (It is written as a play script.). The plot was had a lot of unexpected twists and turns, (SPOILER ALERT) like when Delphi turns on Albus and Scorpius and reveals herself as the daughter of Voldemort. The book is kind of confusing when it repeats the same scenario (The first task in the Triwizard Cup.). I would have to rate it a solid 10/10, but I would love to see it as an actual book.