Harry Potter and the Prisoner of Azkaban is the third book and film in the Harry Potter series. It introduces important new characters, like Sirius Black, Remus Lupin and Peter Pettigrew. For many critics and viewers, Prisoner of Azkaban is the best Harry Potter film. However, others were disappointed with the major differences between the book and the movie. Every adaptation makes changes to the source material, but the omissions and differences in Prisoner of Azkaban turned it into the most polarizing installment. Some regard the film as their favorite, while others have a hard time looking past the big changes from book to film.
Source:https://www.cbr.com/harry-potter-prisoner-azkaban-adaptation/