If one day the villain gets a set of books from which he learns his ending in the future, then he will choose a path to the dark side and use this book to avoid his bad ending and kill all his enemies to continue.
Be a villain. Or choose to use this book to achieve a good ending?
Have you ever thought about what if Voldemort knew everything in advance?
Maybe the second generation Dark Lord will not appear?
Or maybe in the future, the entire European magic world will be under his control.
Concept: Another ending in the parallel world of Harry Potter