From the back cover:
The Power to Believe
Belief is power. The power to believe is the power to create a world rich with magic and wonder. The power to believe is also the power to destroy that world. Welcome to Earth & Sky and Mortal Earth, a world where the beliefs of humankind have spun into being a host of magical creatures, artifacts, and even worlds. The power of our beliefs has given life and human form to the stories of our childhood. They conceal themselves among their creators in the cracks of reality, living their secret magical lives. Fairy tales walk the city streets, dragons are real, and gates open to mysterious worlds...
Now ask yourself--what do you believe?