Another bestselling author for adults tries for the youth market, with all too typically dismal results. Sprinkling references to butts, poop and vomit throughout, Baldacci introduces a nine-year-old inventor who uses “potato-nanotechnology” to turn regular spuds into a quintet of walking, talking, brightly colored giant French fries who help him to rout a gang of bullies armed with paintball guns and to save his dad’s vegetarian burger business. Despite a plethora of cheap laffs, even indiscriminate readers will find the hackneyed characters and trite, slow-moving plot unappetizing. Illustrations not seen. (Fantasy. 9-11)