We Were Liars by E. Lockhart

If a campaign had a book that demonstrated its main theme, this book could be Bernie Sanders' young adult fiction choice.  It is cool, bitter and brutal, as it casts a dispassionate eye on the insular world of the American oligarchy.
Cadence is the eldest granddaughter of a family so rich that they never mention money. Every year, the Sinclairs spend their summer on a private island, where the grandparents have built four houses for themselves and their three daughters, plus a smaller building for their cooks and cleaners.
The Sinclairs are beset by deaths, addictions and the tragedies that afflict all families, however privileged, but they tuck them away behind their strong chins and perfect smiles. Raw emotions are hidden by a curtain of politeness. "I don't know what happened," Cadence says of her aunt's divorce. "The family never speaks of it."
Cadence makes a tight little group with the two grandchildren her own age, Johnny and Mirren, and an outsider, Gat, who joins them every year. Aged 15, Cadence falls in love with Gat. At the end of that summer, she has an accident, a breakdown or some kind of illness, but she can't remember what happened, how or why. All she knows is that she was found on the shore, dressed in her underwear, the sea washing over her. "They tested me for brain tumours, meningitis, you name it. To relieve the pain they prescribed this drug and that drug and another drug, because the first one didn't work and the second one didn't work, either."
That was two summers ago. Now she is returning to the island, to her family, her grandfather, aunts and cousins, and Gat. She narrates the novel, but she doesn't use the polite, restrained style that you'd expect from such an expensively educated aristocrat. The characters are not well-rounded or beautifully drawn; the descriptions are not lush or elegant. The prose is fractured, disordered, messy. This is the voice of a girl who has been broken and is trying to put the pieces back together.
The reader searches with her, combing for clues in the family's behaviour, the lies and omissions of a tight-knit patrician clan.
Of course I won't reveal the twists and turns of the cunning plot, but I can say that when the secret at the heart of the book is finally revealed, it turns out to be nastier and more shocking than anything I had imagined.  But worth it.