I disagree with the major review at the start of these reviews list. I think this is one kind of book if it's to be read by kids 8-12 and another if it's to be read by adults or even by adults to children. What the review above failed to mentioned is that Maurice Sendak actually asked Dave Eggers to publish this novel, and to flesh out the screenplay into a complete narrative. It's clear to me why he wanted to do this.
On one side, for children reading the book, it's a bit dark, psychological, and tense. I think without a parent to mitigate and dampen the effect of the Wild Things' more wild inclinations (wanting to eat what makes them unhappy), I think the book might be a bit overwhelming for the a few 8-12 year olds. I can imagine that it would, however, tickle the minds of many.
This isn't a typical children's story, and it doesn't aim to be, just like the original. It's about complicated childhood drama, and the feelings so many of us have when we want to run away as children. It's about that very real feeling that even in the places we love, we can feel alone, scared, and even betrayed. This sometimes, or in my experience with kids of this age group, leads us to do regrettable, childish things--run away for an evening, hide somewhere for a prolonged period of time, knock stuff over, yell, essentially misbehave. As if the dissolving of structure and certainty makes us want to return somewhere wild, and that's exactly what Max does, and what many of us have done.
But the Wild place is wild for a reason, and I think the idea of the Wild Things Island is so extensive, and painted so broad and perfectly, that it also offers glimpse of our adult wildness, our fears, our excitements, our uncontrolled and bestial tendencies that are sudden jolts of rebellion from the world we create for ourselves.
So, on the other hand, in the large sense, I thought this book was really about growing up, about accepting responsibility, and more keenly for children, about parenting. If read to a child, this book gives an incredibly approachable (for children) account of how challenging parenting can be. I think it can allow children, with the use of metaphors that are comprehensible to them, to see themselves when they are wild, but not feel the guilt of it, and then, as a result, begin to feel an understanding for their parents and guardians as well as what it really means to cooperate and behave.
If you read the book, what I have written, will make a lot more sense. But because of this, I can see why Maurice Sendak wanted the book when his masterpiece already existed, it's because he could only tell so much about subjects that he could only vaguely allude.