Sendak will be best remembered for his children's books, but he also developed productions of opera and ballet for stage and television. And in 2003 he collaborated with playwright Tony Kushner to publish a book and an opera called Brundibar, a story about children in the Holocaust. His works, at their core, were about the same thing, as he told NPR in 1993: "Children surviving childhood is my obsessive theme and my life's concern."
Check out Sendak's recent and hilarious appearance on The Colbert Report:
http://www.huffingtonpost.com/2012/01/25/colbert-report-maurice-sendak_n_1231297.html
