“Those who don’t believe in magic will never find it.” That was the motto of author Roald Dahl, who has made several generations believe in his magical fables.

Take “James and the Giant Peach.” The novel for young readers about a cruelly used little boy, and his escape from heinous relations with a new family of friendly insects, is the kind of magic the late British writer conjured — a little sweet, a little sour, a little edgy and sure to pique a child’s imagination.

The captivating world-premiere musical based on that much-thumbed tome, now at Seattle Children’s Theatre under Linda Hartzell’s appealing direction, delights in dressing up the story in bright colors and jazzy tunes.

And like “Matilda” (a current Broadway hit based on another Dahl book) it stays true to the author by not talking down to kids, and not sugaring up a story that finds its own zigzag route to a happy ending, after some (often humorous) travails.

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The hero of “James and the Giant Peach” is a bright young lad (likable Mike Spee) who loses both of his beloved parents and is placed in the grasp of two very dodgy “aunties” whose idea of child-rearing is turning James into their slave.

The aunts are comic shrews, played with cranky, clowning zest by Jayne Muirhead and Julie Briskman. They glory in nastiness and tear into music-hall-style songs in the blithe, catchy score by the young team of Benj Pasek and Justin Paul (Tony Award nominees for their score for “A Christmas Story,” seen at the 5th Avenue Theatre and on Broadway).

James bonds with gregarious insects — a centipede, a grasshopper, a ladybug — and a dancing worm, all with personality plus. They speak English and come in two sizes: puppet and human. Seattle troupers Kendra Kassebaum, Greg McCormick, Diana Huey, Rich Gray and Heath Saunders make them dandy company — even as they get to squabbling while encased, with James, inside an enormous, seaworthy peach.

Timothy Allen McDonald’s book is adroit (but could shed 10-15 minutes). Along with a charming, well-performed score, “James and the Giant Peach” (staged in an earlier draft at the Goodspeed Opera House in Connecticut) is a real looker, thanks to the eye candy of Carey Wong’s wondrous set, Cathy Hunt’s fanciful costumes and Annett Mateo’s bug-world puppets.

Misha Berson: mberson@seattletimes.com