Daniel Radcliffe has a lot of work to do, being in almost every scene of the movie—except when he's under the invisibility cloak, which gives him a bit of a break. The Harry Potter novels are told in third person, enabling them to explore different perspectives, even if they do center on Harry himself.

The movie follows the same structure, focusing primarily on Harry. In fact, we don't see any scenes outside Harry's perspective in this installment. That allows us to be kept wondering about different aspects of the mystery: what is Hermione up to? Is Sirius evil? Why won't Dumbledore say something straightforwardly? These mysteries are all revealed in time.

Well, except for the Dumbledore one. He stays cryptic until the very end.