The fourth and final title in Voigt's Kingdom cycle (begun with Jackaroo) is thrilling, from its dramatic opener to its stunning climax. Newcomers to the Kingdom books can read it with as much pleasure as fans of the entire series (and without ruining for themselves the surprises of those previous works). Set in an imaginary continent that resembles medieval Europe, the story begins in the brutal realm of the Wolfers, a ruthless people among whom 12-year-old Elske has been raised and, horrifyingly, chosen for a sacrificial death. How Elske escapes this fate is the first of many ingeniously plotted turns, reversals that depend on the heroine's intelligence and determination rather than coincidence or authorial sleight-of-hand. There is much to marvel at. Voigt demonstrates a remarkable breadth of imagination in dreaming up the customs of the various lands Elske moves through; e.g., a Scandinavian-type city builds a thriving economy by hosting biannual ""courting winters"" for young marriageable, wealthy foreigners. The cast also includes a princess wrongfully deprived of a throne (and willing to go to war to claim it) and a man worthy of Elske but chosen for one of the princess's sisters. The characterizations are as sharp and uncompromising as Voigt's readers have come to expect, and the narration never tips the author's hand. This spellbinding work continually challenges readers to keep up with its far-seeing, swift-thinking protagonist. Ages 12-up. (Oct.) FYI: The Vermeer masterpiece that appears on the jacket, Head of a Girl (a painting that also appears this season on the cover of the adult novel Girl with a Pearl Earring by Tracy Chevalier), links Elske with the simultaneously reissued paperback of another novel in the Kingdom cycle, On Fortune's Wheel (S&S/ Aladdin, $5.50 -82957-4), the jacket of which features Vermeer's Woman Reading a Letter.