Yesterday you reminded me of Diana Wynne Jones' Dogsbody, and now I'm on Page 126 and annoyed at having to tear myself away from it. It's worth lingering on Jones' elating 1975 novel because, unlike the latest Potter book, it opens on a disorienting note—something about astral luminaries and effulgencies and a zoi … what the hell? Then it settles into a dog's-eye saga with just enough sci-fi elements to keep you guessing. The surprises on every page are in contrast with the new Potter, which inevitably follows the template established in Rowling's first books. There's a certain pleasure in the ritual and the repetition, but you're right, the structure is "pinching a bit"—pinching the reader and Rowling both.
Shouldn't it pinch, though? The slow opening is meant to drive us crazy, just as Harry is driven crazy by being kept in the dark, maltreated, and unjustly accused of high crimes. In this book, her first since 9/11, Rowling has repeated much of the formula but without the larky stretches. Reader Jeffrey Young writes to say he agrees with you and complains that, "There's far too little joy in the book … and the joys [Harry] does find are both short-lived and come across [to him] as superficial. I had a rough childhood—as rough as any—but I had longer stretches of joy than Harry." I'm sorry about his childhood, and I don't disagree with him. What follows the downbeat opening are typical ghastly high-school anxieties—O levels (or O.W.L. levels), the dreaded "career counseling," and a humiliating and unconsummated romance. Long sections of the book are harsh and punishing, and the whole thing ends on a note of anger and intense grief. The final chapter is called "The Second War Begins."
My response to this is complicated. Although I'm a little sick of the emphasis on war in our big pop-culture sagas—Harry Potter, Star Wars, and The Lord of the Rings—I find the anxiety level of Order of the Phoenix to be startlingly in synch with the mood of the day. I suppose one could argue—as Young does—that children's literature has a mandate to be more escapist. But I think it also owes us a bit of catharsis. There is something healthy about seeing our worst fears realized (for a time). And Voldemort—the "mudblood" aligned with the "purebloods" in a war against mudbloods and Muggles alike—makes a haunting antagonist in an age of escalating illiberalism. (To answer your question about Roald Dahl, Polly: I don't especially like Dahl's way of characterizing peoples' hearts via their body shape. You just know he was tall and good-looking and had a tall, good-looking family. I love a lot of his books, though—even if Draco Malfoy would, too.)
And yes, you were right to speed up the reading: These books are meant to carry you along. Professor Harold Bloom famously found four clichés on a random Potter page and complained that the series' popularity was yet another sign of the imperilment of Western civilization—but professor Bloom didn't have to sit through Charlie's Angels: Full Throttle with me last night. I find Rowling's writing to be dry, witty, and elegantly understated. But there's nothing to linger over.
As you've pointed out, some of the most compelling scenes in the book are with Snape, who saves Harry's life (again) but on whom Rowling never goes soft. The Pensieve flashback—in which Harry views his father's and godfather's egotistical bullying through the eyes of the socially backward young Snape—is a highlight. And then, of course, there is a mythic new beast, the Ministry-approved Defense Against the Dark Arts teacher—the unluckiest job in the world, next to being the drummer for Spinal Tap. She is professor Umbridge, a squat, officious, passive-aggressive ("Hem, hem") monster who only has to smile "sweetly" at Harry to make me remember why I would have shown up at my 25th high-school reunion with a can of gasoline and a box of matches.
Some questions I should label as "spoilers": Were you a little let down, as I was, by a climactic ensemble wand-off that seemed more suited to Star Wars (or sundry Hong Kong sword-and-sorcery epics)? And were you as stirred as I was by Dumbledore's revelation about the dreaded Petunia, which raises fascinating questions about the stabilizing force of a family, even a terrible family, on our lives?