Where the Wild Things Are was, and still is, one of my favorite books. It is my favorite book to give away as gifts, to young children or expectant mothers. I love thinking that the adults remember the book, and remember how much they enjoyed reading it as a child, and then pass that love on to their children. I hope to someday have children of my own, and I will be reading this book to them, you bet your bottom.
But Where the Wild Things Are wasn't his only book. He also illustrated the Little Bear series by Else Holmelund Minarik. In case you don't remember (impossible, I know), Little Bear was the fantastic story of a bear and his family, and the friends he has in his neighborhood. My favorite Little Bear story (at least from the TV series) is when he imagines that he is going to the moon, and meets moon creatures, including one who acts like his mother. Sendak's illustrations brought those books to life for me.
His Wiki page describes his career in more detail, and it includes many things I never knew about him. But the only thing I need to know is, he was an amazing person, a great writer and illustrator, and created one of the most fantastical worlds for me: the jungle, inhabited by Wild Things, visited and conquered by the Max in all of us.