Everyone else may be thrilled about Harry's return, but the teenage wizard himself is in a pretty bad mood. And who can blame him?
The man who killed his parents is back and amassing his troops. Hogwarts has been invaded by the poisonous bureaucrat Dolores Umbridge (picture a toad in a fluffy pink cardigan). And everyone thinks he's either nuts or a pathological liar, thanks to a smear campaign by the Daily Prophet. Oh, and his best friend made prefect and he didn't.
Elites like Harold Bloom sniff at Rowling's prose - and it's true a reader rarely pauses to parse the beauty of a sentence (that would slow you down!). But she tells her tale with such vividness that the words almost vanish as the story pours directly into your consciousness. And whoever thinks that doesn't take skill with a pen, well, get thee to a writing desk.
Harry may be grousing, but there's plenty for fans to cheer. Book 5 isn't spattered with the gore that marred Book 4. And almost every beloved character puts in an appearance, with the Weasley twins swiping the book's most triumphant scene. Ginny Weasley comes roaring back from her role as hapless pawn in Book 2, as does Neville Longbottom from his role as completely hapless. Of the new characters, the punk witch Tonks and the not-as-spacy-as-she-seems Luna Lovegood make particularly welcome additions to the Potterverse.
Reflecting both the teen characters' growing awareness of the world around them and the fact that the stakes are higher now that Voldemort is back in the flesh, Quidditch and school rivalries are all but crowded off the page. (Frankly, it was hard to get worked up about who won the Triwizard Championship in "Goblet of Fire" anyway.)
As the war with Voldemort approaches, adults take a more active role, as in Book 3, still my favorite of the series. And not just as feckless or absent (or evil); Rowling devotes some ink to explaining the mysterious workings of the adult mind. Mrs. Weasley isn't just the scolding-but-loving mum of the prior books. The image of her sobbing in fear for her family while she cleans up the headquarters for the Order of the Phoenix (a.k.a. "the good guys") is one of the most heartbreaking scenes in the book. Readers (and Harry) also get a better understanding of the reasons behind Professor Snape's loathing of the young Potter (although understanding doesn't make Harry like him any better). And even Aunt Petunia seems marginally less odious.
That said, the emotional layering isn't as rich as in Book 3. The widely reported death, while sad, lacks the poignancy of the loss that Harry feels for his parents - or for that matter, that Neville feels for his. And the ending seems hollow: There are no twists or revelations, just confirmation of what readers have long suspected. But that flatness may also stem from the knowledge that once you hit the last page, there's going to be a long wait until Book 6.