In addition to its engaging storyline and themes, "Harry Potter and the Prisoner of Azkaban" is also notable for its vivid world-building and memorable characters. The character of Professor Lupin, a werewolf and Defense Against the Dark Arts teacher, serves as a particularly compelling example of Rowling's skill at creating complex and nuanced characters.
It is funny, scary, beautiful, and deeply moving. It is, quite simply, magic.
Explain the and how they changed the ending.