Profoundly beautiful and affecting, Where the Wild Things Are is a breath- taking act of artistic transubstantiation. From Maurice Sendak's beloved picture book about a rambunctious little boy named Max and the kingdom of untamed creatures who adopt him as their like-minded king, filmmaker Spike Jonze has made a movie that is true to Sendak's unique sensibilities and simultaneously true to Jonze's own colorful instincts for anarchy. This is, to quote the 1963 children's classic, ''the most wild thing of all.'' It's also personal movie- making, with corporate backing, at its best. Whatever the (well-documented) struggles it took to create this gem, the result is worth every monster growl.