We Were Liars by E. Lockhart
The Sinclair family is rich and beautiful. So rich that the patriarch, Harris Sinclair, owns his own island off the coast of Massachussetts and built on it not only a mansion for himself and his wife Tipper, but also 3 additional houses for each of their 3 daughters. Every summer the family gathers for 2 months, and the children of the 3 daughters become very close. After Tipper dies the 3 daughters begin to fight for bits and pieces of the family fortune, placing their teenage children right in the middle, and Harris encourages the bickering until it becomes almost unbearable for the grandchildren to be there. An "outsider" enters the family through the relationship of one of the sisters and she begins to bring his nephew Gat each summer. But something happens the year Cadence turns 15. She is found wet, cold, barely dressed on the sand on Tiny Beach and because of a suspected head trauma has lost all memory of that summer. Cady is now 17 and returning to the island for the first time since the accident that caused her amnesia. The Sinclairs may be rich and beautiful, but it is a severely disfunctional family with secrets to hide.
Set aside a whole afternoon for this one, because once you start reading you will not want to put it down. Cady tells fairy tales throughout the story about a king who had 3 daughters, and the stories get more and more gruesome as they go on and tell a story of their own. The ending is satisfying and surprising. The story is told in beautiful lyrical language by Cady, who gradually begins to remember bits and pieces of that tragic summer. Read it and pass it on, but do not give away the ending!