"The Amber Spyglass" is the final book in the most ambitious allegory being published today, Philip Pullman's "His Dark Materials" trilogy. With epigraphs from William Blake, Rainer Rilke and John Ashbery, and tributes to John Milton and Henrich von Kleist in the acknowledgments, Pullman places himself in a tradition of serious symbol makers, which might be expected to intimidate the children to whom the series is directed (or, at least, to whom it was directed when he began it). But while Pullman may have become caught up in adult theology -- and while he has won more grown-up readers with each "Dark Materials" book -- he keeps the swooping plots and passionate characters that make his earlier books so appealing to young readers.

With fantasies, as with mysteries, the hardest part to get right is the end, where everything is revealed. The magical objects and unexplained forces that flourish in the genre easily lend themselves to anticlimax, disintegrating into mere mechanics or bluster once the author attempts to explain them or tie them together in the traditional apocalyptic battle at the end. Given the delicious promise of the first two "Dark Materials" books, some disappointment was almost inevitable. But "The Amber Spyglass" delivers surprisingly little of it; the latest novel is nearly as satisfying as the first two.

Each volume revolves around its title doohickey, while introducing child heroes, magical universes and mythic creatures. In "The Golden Compass," the object is a mechanical device for seeking spiritual as well as physical direction. It belongs to young Lyra, an apparent orphan who lives among dons in an Oxford that somewhat resembles our own. In her world, though, people come in two parts. Everyone has a daemon -- a talking animal companion that's born with him and vanishes when he dies. It's sort of like getting to keep your soul as a pet.

Children's daemons can change shape at will, flitting from butterfly to dog to mouse, but once you hit adolescence your daemon settles into a fixed form that expresses your essence. Daemons are Pullman's best invention. Everything about them seems exactly right, from their childhood mutability, to the fact that your daemon is always the opposite sex, to the way the daemon-person pairs echo and enhance each other. People and their daemons stick close to each other; the only folks who can spend more than a few moments apart from their daemons are witches. When Lyra discovers that someone's kidnapping children -- including her best friend -- she sets off on a quest that carries her to the far north, home of witches and armor-clad bears.

"The Subtle Knife" introduces a new hero from our own world, Will, whose physicist father vanished mysteriously years ago. When sinister men come looking for his father, Will knows they're threatening him, too. An urgent sense of danger propels him through a window into another world, where he finds Lyra and another of Pullman's wonderful inventions: the title object, a knife so sharp it can cut through the substance that separates universes -- and can kill daemons and angels.

Maya Angelou reads from "The Heart of a Woman"