Chris Van Allsburg is always in a dialogue with Maurice Sendak. The greatness of "Where the Wild Things Are" grows out of its mystery: Did Max travel or did he not? If he didn't, why did his mom overlook him when she brought food to his room? And why is the moon different in the final image of Max's window? These (I think) are questions that inspire Van Allsburg. In "The Polar Express," the little boy continues to hear the ringing of his bell after all others can no longer hear. Is this because of a special knowledge that the boy has (or is it just that the boy is slightly deranged)? ....In the final moments of "Jumanji," Peter and Judy notice two friends with the dangerous game board. Should they speak up--or is their memory somehow "false"? What might happen if they stay silent? My favorite of the ambiguous Van Allsburg endings is in his first book, "The Garden of Abdul Gasazi." For a long while, young Alan has felt convince...