It says this is one of the few books to show the humans in illustrated form, but I've seen quite a few books that have illustrated the humans. Ernie's Neighborhood, Ernie's Little Lie, Susan and Gordon Adopt a Baby, I'll Miss You, Mr. Hooper, The Sesame Street Word Book, Big Bird Brings Spring to Sesame Street, The Origins of Super-Grover, Everyone Makes Mistakes, I think humans were depicted in It's Not Fair and Meet Mr. Snuffleupagus, and I'm pretty sure there was an early book focusing on Matt Robinson's Gordon (can't remember the title). David was also in a book that I think was titled Welcome Home, Big Bird, and I think I saw Mr. MacIntosh drawn in Big Bird's Red Book.