Several months have passed since Pearl Rose became Princess Twilight's new Personal Student, and the young Pegasus couldn't be happier. Even if her teacher can be a bit quirky.

One day, while Twilight is out on princess business, Pearl stumbles across an odd book that she's never seen before. Not that unusual with the unofficial Princess of Books herself. But lies inside will open up a whole new world to Pearl.

A world on the other side of a certain mirror, and a brand new hobby that makes her usual reading look rather small by comparison.