Harry Potter and the Order of the Phoenix
Good things:
Good thing #1: Harry takes an important step in teaching the other kids about defence against the dark arts.
Good thing #2: The children work together at the end to face their fears and their enemy. (it just took too many pages to get there)

Bad things:
Bad thing #1: 800 pages; The pacing and feel of this book made me want to scream several times GET ON WITH IT! (the movie version will have the good bits and be much more bearable)
Bad thing #2: Children's Book?; This is the darkest book of the lot so far. If this book had been J. K. Rowling's first it would have been clearly stacked in young adult.
Bad thing#3: Rowling needs a new villain or needs to do something to make Voldemort more interesting.

Overall:
I must be becomming a muggle. I didn't like the Order of the Phoenix very much (although I think it will make for a decent movie)