Oligarchy by Scarlett Thomas
Oligarchy is the fierce new novel about power, privilege and peer pressure from the bestselling author of The End of Mr. Y.
When Tash, daughter of a Russian oligarch, is sent to an English boarding school, she is new to the strange rituals of the girls there. Theirs is a world of strict pecking orders, eating disorders and Instagram angst.
While she spends her time with the other girls at the lake and the stables, a hand-picked few are invited to join the Headmaster at his house for extra lessons. Then her friend Bianca mysteriously vanishes, and quickly the routines of her dorm-mates seem darker and more alien than ever before.