As someone who never read the books this is the worst movie

Actually Deadly Hallows Part 1 is the worst, but you can say that's the first half of a 5 hour film.

Anyway,

Half-Blood Prince spends too much time in the teen romance (which is pretty well made to be honest), but not for everything else.

For example the whole book plotline is useless. Harry finds the book, makes a potion, learns an new spell and we never see the book again. In the end Snape reveals he's the Half-Blood Prince and that's it. Really? They didn't even explained why he calls himself that.
Drako spends the entire movie looking at a vanishing cabinet only to have the big twist that it's... a vanishing cabinet.
The main plotline about Tom and the horcruxes is so simple. Basically we spend the whole movie for a memory. That's it, that's the whole thing.
And when the memory is revealed then all of a sudden Dumbledore becames an expert in Voldemort's horcruxes.
The ring comes out of the blue, but the worst is the locket.
How Dumbledore knew where the cave was? Nothing is explained.


Like I said I haven't read the books, so keep in mind this is a critique of the movie as a standalone film and not as an adapataion.