There's a line in a wonderful newish Norwegian novel  (Out Stealing Horses) that I think applies to Where the Wild Things are:  You decide when it hurts.  In this case, you decide when it's scary.  And I think Bruno Bettelheim in The Uses of Enchantment would say that a book like this allows kids to get fears over with by reading about them.  They can be frightened in the book, and then don't have to be at night.  Oh, and for adults, the wonderful drawings.