It's been two years since Peter Nimble and Sir Tode rescued the kingdom of HazelPort. In that time, they have traveled far and wide in search of adventure. Now they have been summoned by Professor Cake for a new mission: To find a 12-year-old bookmender named Sophie Quire.

Sophie knows little beyond the four walls of her father's bookshop, where she repairs old books and dreams of escaping the confines of her dull life. But when a strange boy and his talking cat/horse companion show up with a rare and mysterious book, she finds herself pulled into an adventure beyond anything she has ever read.