So I saw Harry Potter and the Deathly Hallows Part 2, and it's, for the most part, an accurate adaptation of the last half of the last book.
In some ways this isn't a good thing.
First of all, in the sixth book (there will by many, many spoilers by the way) The Sorting Hate hints at how all four houses must come together to fight Lord Voldemort, hinting that most of Slytherin will join Harry and his friends in a big climactic battle.
This doesn't happen in the movie OR the book. This may sound strange at first, but then I remember hearing that J.K. absolutely refused to hire any editors for her last book and good lord does it show in terms of continuity! Instead, every. single. student that's a Slytherin is shown to be unambiguously evil and more than willing to turn Harry over to Voldemort. In a series that's unmistakably about how terrible racism is that's pretty terrible. Look, I know that The Sorting Hat sorts students according to personality and not race or blood or whatever, I can accept that...except when The Sorting Hat specifically said 'All four houses should come together!'. I mean, why even say that when you KNOW that everyone in Slytherin loves Voldemort? Unless, of course, J.K. messed up in a huge way...a huge way that could have been avoided with, say it with me,
The movie does the exact same thing because it absolutely refuses to seperate itself from the source material, even making it worse by sending everyone in Slytherin to a dungeon...even though in the movie only one person from Slytherin says she wants to turn Harry over to Voldemort...and the rest of Slytherin just kind of shuffles awkwardly...and the guy running the dungeon would love nothing more than to torture people.
You really have to feel for the poor people forced into following material that was in terrible need of a few
Also, remember how Dumbledore had this huge subplot in the seventh book about how he's kind of a b****** and explains why he's dying? Not in the movie at all except, for some reason, he's still just sort of dying. Not really mad about that, it's just a weird decision. If I were making the movies I'd just have Dumbledore not be dying (since I'd have to remove the explanation for it anyway) and tell Snape to kill him so that Malfoy wouldn't have to: not only does it not hurt the story in any way but we now don't have the audience going "Umm...why is his hand like that? What is he dying of? ...never gonna explain that, then?"
Luckily, the movie did two things much, much, much better than the book. For one thing Voldermort and Harry don't have a terrible, takes-you-right-out-of-the-final-climactic-battle-of-the-series, discussion about whether or not Harry Potter is, in fact, a Gary Stu. The writers for the movie realized that having your main villain sound like a whiny a**hat talking about which Trek Captain is the best (Picard, by the way). For two, Harry's adopted son doesn't have My Little Pony hair (FiM is awesome by the way).
Also, hilariously, Harry's son worries about being in Slytherin, just like in the book! Harry's response should have been "Well son, when J.K. wrote this epilogue years ago the whole 'being in Slytherin is okay' thing would have paid off in some significant way...buuuuut because she didn't hire editors to follow up on continuity I set up in book six and the entire d*** premise of the series then you'd better pray to high heaven you don't end up as an evil, evil Slytherin!"
So the movie was okay, but needed to get rid of some of the stupidity of the book it was based on.