I am so, so happy that I prohibited the boys from seeing any of the movies before reading the books; and I feel so, so sorry for anyone who’s only ever seen the movies and thinks they know the stories. Naturally there are a lot of great scenes and there is a lot of rich detail that never made it into the movies, but that is true with any novel adapted for the screen. Also as with any adaptation, some of the changes made by the filmmakers were improvements on those unavoidable parts of the books that were not great or rich.
But the films do worse than leave out scenes and detail — they get key characters wrong. (Or at least, numbers 1 through 6 do. None of us has yet seen parts 7a or 7b.) The film Dumbledore may be a powerful wizard, but he has none of the book Dumbledore’s warmth, deep wisdom, or mischief. And Harry Potter may stir himself to heroic action on film when the need arises, but there is no sense of the fierceness of purpose to which he is so often roused in the books.
I’m sure countless Harry Potter fan sites have debated these things endlessly so I won’t belabor them, but I can’t let it go before giving one example to illustrate my complaint. Spoilers ahead.
In the climax of book 6, Harry and Dumbledore return to Hogwarts castle and realize they’ve stumbled into a trap. They can hear Voldemort’s agents coming. With only seconds to spare, Dumbledore orders Harry to conceal himself, and then uses the last possible instant to cast a spell that magically paralyzes Harry, so Harry won’t give himself away during the events that Dumbledore knows are about to transpire. Casting that last spell costs Dumbledore the chance to defend himself, as in the next instant another spell disarms him, a spell cast by a lesser wizard who normally could never dream of getting the drop on Dumbledore. But Dumbledore knows — as do we — that Harry, loyal and brave, is constitutionally unable to remain in hiding while Dumbledore is under threat, and so he willingly sacrifices his own defense to ensure Harry’s safety.
The film version of that scene plays without any of that characterization. Harry goes into concealment and remains there of his own volition even during the terrible events that follow. Dumbledore is disarmed effortlessly. The scene tells us nothing about either person.