He changed not only children's books but the whole idea of storytelling. "Where the Wild Things Are" is one of those literary watermarks. Impossible to ignore, and, so far as I know, not yet topped.
It's a fairly obscure place. For those who don't know, A. S. W. Rosenbach was one of the world's premier rare book dealers in the first third of the 20th century. Among other coups, he brokered a significant number of Shakespeare First Folios, a couple of Gutenberg Bibles and acquired James Joyce's handwritten manuscript of Ulysses ( which is in the museum's possession ).