A Great and Terrible Beauty by Libba Bray

When Gemma Doyle, a British girl living in India, watches her mother's sudden and puzzling suicide, her life changes. Gemma travels from India to England, and she begins her new life at an all-girls' preparatory school. At first Gemma feels very out of place in the midst of stringent etiquette and cruel classmates, but soon finds herself becoming friends with unique interests. They discover a long-lost diary, which they seen realize holds the truth to the mystery that has been puzzling them.

This is one of Libba Bray's best books yet!