This one looks a lot better than the previous two (visual effects, cinematography, production design). It also got superbly-realised characters in the form the ghost-like creatures, the Dementors. This, and a few others, were interesting concepts, but given the movie (book) is targeted for children, the exploration is not satisfactory enough, and the humor silly, perhaps to help make things less scary. I also found the more grown-up children more interesting, most especially the clever girl, one of the 3 best friends.
The concept of time travel is given quality treatment, though it remains silly, as is usual with time travel stories.
This is the best in the series.