Four fifth-graders are recruited by a scheming magician in this hefty bonbon from the author of the Fablehaven tales. At first, Nate, Summer, Trevor and Pigeon think they have it good. Having asked them to help her recover a hidden treasure that (she says) belongs to her, Belinda White, friendly proprietor of a sweets shop that has just opened in their small town, provides some uncommon candies--like Moon Rocks, that give them the ability to jump like grasshoppers, and literally electrifying Shock Bits. When she begins asking them to commit certain burglaries, though, their exhilaration turns to unease, and rightly so; Mrs. White is actually after a draft from the Fountain of Youth that will make her the world's most powerful magician. And, as it turns out, she isn't the only magician who's come to town--not even the only one whose magic is tied to sweets. Filling out the supporting cast with the requisite trio of bullies, plus magical minions of various (and sometimes gross) abilities, Mull trots his twist-laden plot forward to a well set-up climax. Leaving the door open an inch for sequels, he dishes up a crowd-pleaser as delicious--if not so weird--as Charlie and the Chocolate Factory . (Fantasy. 10-13) Copyright ©Kirkus Reviews, used with permission.