Marnie Plummer is a bookish, lonely girl with a chip on her shoulder. There's nothing she cares about more than her favorite book series, The Griffon Riders of Crystalfall. When it miraculously turns out that the world of the books is actually real, and they need a Chosen One to come from the real world and save them from danger, Marnie is shocked and-of course-overjoyed.

There's just one problem.

The Chosen One they seek is not actually her-it's Tiffany Rodriguez, the pretty, popular girl who (in Marnie's eyes) already has everything she could ever want. Why should Tiffany get to have this, too? Marnie decides she's the one who deserves to be the Chosen One. She'll make it happen no matter what, even if she has to do something she'd never thought she could do: become Tiffany's friend.