High Wizardry, the third book in Diane Duane's wonderful Young Wizards series, that it barely counts as fantasy. Which is entirely awesome; this is the Diane Duane whose name I saw with pleasure and anticipation on those Star Trek novels of my youth, except even more cosmic. More cosmic in every possible way.
I've praised Duane's scientific/mathematical approach to magic before, but little did I know just how scientific and mathematical it was yet to become. For, as the focus shifts from Nita's and Kit's explorations of the powers and responsibilities of wizardry to Nita's astoundingly precocious and fierce little sister Dairene's, Duane adds an important new tool to the mix: computers. As in when Dairene starts investigating this amazing new world that her sister finally had to come clean about in Deep Wizardry, her version of the Wizard's Manual shows up on the family's new Apple computer, which Dairene of course already knows how to put together and program even as her parents are carefully sorting through what order in which to Read the Fine Manuals.
Lickety split, Dairene has taken the Oath (every wizard must promise to protect life and delay entropy with all his or her power, with her very life if need be) and is programming spells of genius-level complexity. The world all but quakes; the younger a wizard is, the more raw power he or she can command, and Dairene is the youngest, smartest wizard ever. The youngest, smartest wizard, with a fixation on outer space and Star Wars and finding her own Darth Vader to fight. Which means soon she is computing her way to and through outer space, with each jump getting progressively farther and farther from home until she's in another galaxy -- with her danger growing at each jump.
Nita and Kit and their mentor wizards' red and blue macaw, Picchu (wizards' pets get strange over time, and Picchu is something of a sibyl) more or less to the rescue, but by the time they catch up with Dairene, she is on the verge of having things pretty much under control. Having discovered a planet that's one giant computer chip, awakened it to sentience and taught it to create artificial life and all. You know, nothing but a thing. Except oh, there's her Darth Vader, except her Darth Vader is a million times craftier, more subtle and, yes, more powerful. Gulp. Okay, maybe a little help.
So again, it kind of drives me nuts that the Harry Potter books, with their elitism, their ugly "muggles vs magic" divides, their contempt for the world, were the ones to get popular, and these have remained as obscure as they have. In the universe next door, which I so long to visit, these got made into big CGI blockbusters and all the kids strive to emulate Nita, Kit and Dairene by cultivating their intelligence, exercising their imaginations, and thinking their way out of problems. Ah, me.