''Harry Potter and the Half-Blood Prince" hangs on the two great and abiding themes of lasting literature: love and death. What is most admirable about this, J.K. Rowling's sixth book of the seven intended, is her unswerving dedication to these two primal elements, and her affirmation of their central position in human lives.
On the light side -- lightness being slimmer than ever in this darkening series -- there is a great deal of talk about love. The young heroes and heroines of the Potter series are now 16 and 17, and so they ''snog" and ''hook up" with one another, break up, and rejoin, in an almost bewildering romantic dance. There's an impending wedding between Bill Weasley and the ravishing but irritating Fleur Delacour. We hear about the dire effects of unrequited love, of hasty or ill-matched marriages. The Weasley twins, Fred and George, in their now-popular joke shop, Weasleys' Wizard Wheezes, sell Patented Daydream Charms and the ''best range of love potions you'll find anywhere."
The book also focuses on the love of a parent for a child, of a teacher for a student, and on the surprising and inevitable romances among some of the main characters. The tale ends with the promise of a wedding, that most common ending in comedy -- and yet one would hardly describe this book as comic.
Indeed, beneath the seemingly smooth surface of the book's more than 650 pages lies a new charge of gloom and darkness. I felt depressed by the time I was two-thirds of the way through, and thoroughly so by the book's end, despite its clarion charge against despair. As Albus Dumbledore, headmaster of the Hogwarts School, advises concerning the evil Lord Voldemort: '' 'There is nothing to be feared from a body, Harry, any more than there is anything to be feared from the darkness. Lord Voldemort, who of course secretly fears both, disagrees. But once again he reveals his own lack of wisdom. It is the unknown we fear when we look upon death and darkness, nothing more.' "
As usual, Rowling's powers are startling, beautiful, original, wholly inimitable. The book bears the mark of genius on every page. Even in her occasional moments of awkwardness, the force of her imagination bears us up. Landscape, in this book, is like that of Charles Dickens's London -- brooding, broken, gold-lit, as living a character as any other. Similarly, her depiction of minor characters can be breathtaking: ''Narcissa threw back her hood. She was so pale that she seemed to shine in the darkness; the long blonde hair streaming down her back gave her the look of a drowned person." Rowling's grand effects are more sweeping and jubilant than ever, even while the sorrows and darkness reach deeper: ''Dumbledore then waved his wand again, and the front door opened onto cool, misty darkness. 'And now, Harry, let us step out into the night and pursue that flighty temptress, adventure.' "
All the same, there has been a sea-change over the past few Potter books, beginning with the opening scene of the fourth, ''Harry Potter and the Goblet of Fire." It is the difference between fantasy, which was the territory of the first, second, and most of the third books, and horror, the new territory now entered in earnest.
It is hard to pinpoint the exact differences between fantasy and horror, of course, and, like any other genre, there are blendings that make that distinction still more difficult. But by and large I would say that fantasy creates an alternate universe, complete with its own rules and magical beings. The struggle in fantasy is between large forces of good and evil, such as we encounter in J.R.R. Tolkien and C.S. Lewis. Horror fiction is darker, bloodier, more gory, and less rational. It is, in fact, the landscape of bad dreams, as in: ''There was no waking from his nightmare, no comforting whisper in the dark that he was safe really, that it was all in his imagination . . . he was more alone than he had ever been before." One can argue endlessly whether horror fiction is good or bad for the young soul -- surely, it is not coincidental that a blurb from Stephen King is featured on the book's flap. But I'm not sure that horror will nourish those young faces I saw gleaming outside the bookstore early Saturday when the book was released. Some young people will embrace this new darkness, while others will feel disenchanted, even disinherited. No one knows exactly where Rowling is ultimately heading with her series, but she has certainly turned a corner here.
There are still the delightful moments of legerdemain: ''The furniture flew back to its original places; ornaments reformed in midair, feathers zoomed into their cushions; torn books repaired themselves as they landed upon their shelves; oil lanterns soared onto side tables and reignited. . . ." There are glorious decorative effects, at which Rowling is particularly ingenious: ''The ceiling and walls had been draped with emerald, crimson, and gold hangings, so that it looked as though they were all inside a vast tent. The room was crowded and stuffy and bathed in the red light cast by an ornate golden lamp dangling from a corner of the ceiling in which real fairies were fluttering, each a brilliant speck of light."
Voldemort does not so much as put a toe into the book, except as memory. Harry has more to do with Dumbledore than in any previous book, so those who missed the headmaster's presence in the past two will enjoy the scenes that Harry and Dumbledore share in private tutorials: '' 'What will you be teaching me, sir?' 'Oh, a little of this, a little of that,' said Dumbledore airily." Dumbledore dispenses more wisdom here than in previous volumes, as if he too is in haste to prepare Harry for the final battle waiting in the seventh.
Having finished the book -- and being bound to the unspoken promise that the reviewer reveal no key plot details -- I worry about those happy young faces at the bookstore. They are in for the smoothest sailing yet through the bulk of the book, and a very rocky ending. Rowling does not spare her readers much.
As for the book's violence and gore, the horror and sorrow in some of its scenes, one may hope that young readers are better prepared to face such darkness than we sometimes suppose. Children's author Maurice Sendak once commented, ''The one question I'm obsessed with is, How do children survive?" He did not believe that children always needed protection from their fears and nightmares. Youth has the infinite power of hope. As Dumbledore reminds us, ''Age is foolish and forgetful when it underestimates youth." Liz Rosenberg writes children's books and teaches at the State University of New York at Binghamton.