Harry Potter and the Order of the Phoenix was a horrid adaptation of the book, and not worth seeing whether you read the book or not. Here are the two possibilities:
One, you read the book, and you understand everything that happened in the book and want the illustrative Cliff’s notes version and have no imagination.
Two, you didn’t read the book, and want to know what happens next. The movie won’t make any sense, because it’s too abridged.
Either way, it’s not worth your time, skip it. Especially when compared to the brilliant interpretation presented by the previous film. 4/10.