So I read this book, well  listened to it in audiobook format actually, and really enjoyed it. At the beginning I was a little critical because it seemed to me like a steryotypical young adult book but once I gave it a chance it proved its worth. 

       Three Dark Crowns by Kendare Blake, is about triplets who are all born to be queens but each belongs to a different group: The Poisoners, Elementals or Naturalists. It's the story of three sisters who growing up, know they will have to kill eachother to win their throne; because it has always been this way. But when Arsinoe and Katerine, a poisoner and a naturalist, possess very weak powers and their sister Mirabelle, a favorite of the temple, is believed to be one of the most powerful Elementals in history,the Queens trial, the game in which only one sister immerges a Queen, is questioned and much more sinisters means to the throne are envisaged. Who will survive and immerge victorious?

Unfortuneately not at the library yet but check out reviews and a descrption at Goodreads  

https://www.goodreads.com/book/show/28374007-three-dark-crowns