I'm going to do something I've never done on this site before: give a 'negative' review.
I did not like the Tale of Despereaux by Kate DiCamillo. But the reasons I did not like it are precisely the reasons why children will/do.
I've been reading fantasy since I was a child. I no longer need 'help' in feeling I'm inside the novel. Kate DiCamillo employed a writing style wherein she asks the reader to 'picture' things or 'feel' things. She also addresses the reader so often that, for me, it made it harder to stay in the story. But this is just the sort of language that helps kids feel like they are participating in the action. In fact, I imagine reading this story to a child would be a lot of fun.
Another thing that made it hard for me was the constant starting and stopping of the story by way of introducing another main character. This is not a story that reads linearly. There are three beginnings. Each one brings the reader up to speed about the lives of the characters - Despereaux (the tiny mouse), Roscuro (the evil - or not so evil - rat), and Miggery Sow (the unwitting facilitator of Roscuro's revenge). Again, for children, this works.
The chapters are all short, adhering a child's attention span. And any difficult words introduced are also explained within the text, making this a potentially good reading primer for young children.
Finally, the writing is superb. If you're an adult reading this to yourself, well, it's a matter of taste. But I'd suggest finding a child to share the story with. There are several fun characters if you like telling stories with 'voices'.