Twelve-year-old Leo is a pragmatist. He doesn't believe in magic until a mysterious book, Grimmoire's Fairy Tales, falls off a library shelf and hits him on the head. When he opens it, he sees his own name and likeness in the story of "Leo and the Sunken City." He is not just a reader; he is the main character of the book's final, unfinished tale. The only problem? The villain of the story, the Gloaming King, knows he's in an unfinished book and is manipulating the plot to break free from the pages, which would unleash his eternal night upon the world. Leo must navigate the story's rules, team up with the book's other characters and figure out how to write a satisfying and powerful ending before the Gloaming King succeeds.