From this very nice site centered loosely around the new Wild Things movie, some perspective on how ground-breaking (and/or disruptive of the social order) Sendak’s book was on publication, from children’s librarian and scholar Sheila Egoff.
While the illustrations disturbed those adults who saw the “Wild Things” as ferociously threatening rather than humorously subservient to Max’s will, the extreme reaction to Sendak’s work intimated that there was more at stake than a matter of interpretation of the pictures. As it turned out, this as yet unformulated anxiety was justified. Sendak’s underlying theme that a child has unconscious needs, frustrations, and fears unsettled society’s hitherto conceived ideals of early childhood and the book itself broke the stereotypic mold that had held for almost a hundred years.