Harry Potter is a child wizard. He is special because, although his parents were killed by the evil Lord Voldemorte, he somehow managed to survive. He attends a school for young wizards called Hogwarts, is always getting caught up in all types of mischief, and still finds time to save the world, usually due to a) his friends b) a dues ex machina or c) both.
This oversimplified capsule of Harry Potter might make it sound like I don't like the series, and that's not true. I didn't pick up Order of the Phoenix because I liked the title; no, I've read the other four Potter books and decided I'd read the last two so I could read book seven when it comes out, thus avoiding having the book spoiled by Yahoo which will no doubt run a headline announcing the book's final twist days after its release. And so, I did. Also, I was in Salisbury, North Carolina without a car.
Order of the Phoenix is too long. The first 200 pages could have been condensed to 50 pages or less without losing anything vital. As a result, I was nearly halfway through the book (which clocks in at a hefty 850ish pages) before I really got involved. The second half was some of the more intense writing of the series, but it doesn't change the fact that the first half is 75% filler.
Much like Song of Susannah, anyone reading the Harry Potter series will no doubt read Phoenix, and if you enjoyed the rest of the series, you'll probably enjoy about half of this book. And, that's all, at least until I finish War and Peace. Cheers.