The fifty-year birthday of a good children’s book marks a real passage, since it means that the book hasn’t been passed just from parent to child but from parent to child and on to child again. A book that has crossed that three-generation barrier has a good chance at permanence. So to note the fiftieth birthday of the closest thing that American literature has to an “Alice in Wonderland” of its own, Norton Juster’s “The Phantom Tollbooth”—with illustrations, by Jules Feiffer, that are as perfectly matched to Juster’s text as Tenniel’s were to Carroll’s—is to mark an anniversary that matters.