The Game, Diana Wynne Jones

Hayley is supposed to be living with her grandparents, but her grandmother gets really mad and sends Hayley away. Hayley isn't even sure what she's done, and all of the hustle and bustle of her cousins is kind of confusing. But then they play the Game, and it turns out Hayley is really good at it.

Lots of mythology in this one, kind of tangled up and rushed. Still fun to read.