The great good thing - Roderick Townley

Sylvie is eternally twelve years old and has been a princess for more than 80 years, ever since the novel she lives in was first published. But she longs to break free of the never-ending adventure. It's not that she doesn't like her story - she does - it's great - she's the heroine and it's full of excitement. But the trouble is that it's always exciting in the same way, and although Sylvie loves her storybook friends and family, she's getting bored.
Then after many years of neglect the book is opened and, as a new reader gazes down into Chapter One, Sylvie breaks an important rule for all storybook characters - she looks at the Reader.
Worse still, she gets to know the Reader, a shy young girl called Claire. And when Claire falls asleep with the book open, Sylvie enters the girl's dreams and discovers a new and exciting world. A world where adventures are rewritten daily, and dark, unpredictable dangers lie in wait - and where Sylvie must achieve one great, good thing to save the lives of everyone she loves.