It probably wasn't fair to read this just after that Tamora Pierce book, because poor Tamora can't compare. DWJ's voice is just so strong, and her story structure is so well thought out. She's one of my writing heroes. When I'm trying to put together a story, I often come back to Chrestomanci, and the way there are so many small crises that all build up into one frenzied conclusion.
This book was in the Children's section of the library, and "Sandry's Book" was in the teen section, but I would say "Power of Three" had a much more complex writing style. The sentences are more varied, there are more commas.
The book mainly is about three children--two who have talents and one who thinks he doesn't. They live in a society reminiscent of celts in fantasy literature (not real celts). They are in a constant war with the Dorig, another species who live underwater, and are in constant fear of the Giants. Well, the giants turn out to be us, and the Dorig turn out to be pretty similar to the "people". Well, the three kids wind up meeting two Giants, and then two Dorig, who are about the same age as they are, and have to work together to save the moor. Or at least, the giants and "people" want to save the moor. The Dorig would greatly benefit from the moor being flooded.
It reads like a myth, like something out of the oral tradition. I would love to read this book out loud, there are so many statements that want to be said not just in my head. They often argue about who gets to call themselves "people" and other rather complex questions like that, which was to me kind of reminiscent of that quote I saw so much in the last week from Madeleine L'Engle, about how she wrote children's books that were too difficult for grown-ups to understand.
As an aside, it's interesting that the grownups who grew up reading that stuff are now being accused (i.e. in the media and the like) of not being willing to grow up. It takes us longer to accept that we have to get a real job, and move out of our parents' homes, and have kids, and then when we do we teach them to like The Pixies and buy comic books to leave around the house to encourage them to read. There's probably a rant in there somewhere, but I'm pretty sure I'm not the one to write it.
Anyway, this book seemed out of that tradition. I totally recommend it.