Graveyard shakes
(Book)

Katia and Victoria are sisters and scholarship students at a private boarding school. While Victoria tries to fit in, Katia is unapologetic about her quirks, even though their classmates tease her. After a big fight, Katia runs away from school. And when Victoria goes looking for her, she accidentally tumbles into the underworld of a nearby graveyard. It's inhabited by ghosts and a man named Nikola, who's preparing a sinister spell that's missing one key ingredient.