I'm surprised that some have never heard of the book. It is a children's classic. If you haven't read it to your kids, I really encourage you to go out and buy it (or borrow it from the library). It really is a nice story and can be read in less than 10 minutes. It was one of my favorite books, and it's now my sons favorite. They can recite it by memory.
I'm sad to see this movie getting bad reviews, since we are huge Maurice Sendak fans in my house. We'll go out and see it today, but I'm prepared to be disappointed. Then we'll probably come home and watch the cartoon version of the book made by Scholastic books Dvd's. It is an exact duplicate of the book with a narrated voice. My kids still love it.
I guess we won't be seeing Sendak's "In the Night Kitchen" made into a movie now. Another one of his great stories. Oh well.