From the promotional copy:
And sometimes the Strange came to visit Clare, and dreams walked through her waking life.
Clare Macleod and her father are returning to Ireland to the house where she was born: a house under a green hill, with a tree inside it.
Inside the tree, she finds long-forgotten companions of her childhood: a world made of living lights, and a boy named Finn.
But unless Clare and Finn can defeat an ancient, furious foe, their two worlds will be ripped apart, severing the human world from art and dreams forever.
An adventure story about finding the courage to make—to write, draw, invent, dream–and the courage to throw yourself on what you fear and let it bear you up, the way the wind bears up the birds.
There is no safety, and so we must touch and be touched, and we must fall and fly.