It seems very simple and even slightly cliché as everyone has at least heard of the material it is based off of but it is actually a very complex story with real character. The film lets you, the audience, experience just enough time with each monster and they all feel very unique with differing backstories and relationships with one another. It turns what was once just a basic children's tale to a very serious and even sometimes adult movie with themes that many younger kids won't be able to connect with right away. Themes of dealing with depression and anxiety, being afraid to express yourself, feeling that you don't have a say in anything. This is still a kids' movie at heart, though. There are a lot of fantastical scenes that can be done because of the audience's belief that all of this is taking place inside Max's mind. In this fictional world, there can be a desert right outside of a forest which is also right outside of a mountainous region which also happens to be bordering a beautiful beach. It gives the sense that anything is possible in this world and creates a great suspension of disbelief.
One thing that I personally loved about Where The Wild Things Are is the blend of practical effects and CGI. All of the "Wild Things" are just men in well-made suits but the facial movements are done with CGI to make the creatures look real. The soundtrack also fits perfectly with the theme of the movie and will stick with you well after you've finished.
Where The Wild Things Are is wild!