We Were Liars By E. Lockhart

Cadence Sinclair spends her summers with her wealthy family on a private island just off the coast of Cape Cod.  They spend their summers in the various houses on the island.  Cadence and her cousins, Johnny and Mirren and their friend Gat have been spending their summers on the island since their age eight.  They live together in luxury taking care of "the Littles" or their younger cousins and enjoying the beautiful beaches, until on their fifteenth summer on the island Cadence has a mysterious accident at night spinning her perfect life around.  Cadence becomes sickly and spends the next few years in a haze of amnesia, horrible headaches, and drugs.  She can't seem to remember anything about her accident.  Why was she swimming alone at night.  Why was she in nothing but her underwear.  Cadence just can't remember.  This is addictive with twisting suspense and gut wrenching truths.  I would recommend this book to grades 6 and up.