Bonjour Tristesse by Françoise Sagan.

On vacation in the south of France, Cecile and her youthful, philandering father Raymond are spending a leisurely, hedonistic summer in a rented villa. With them is Raymond’s mistress of the moment, Elsa, a beautiful, red-haired woman almost half his age whom Cecile finds entertaining but rather simpleminded and nonthreatening to her companionable relationship with her father. The three of them spend lazy days swimming and lolling on the beach, and they dance and drink at the casinos into the nights. Cecile, over-indulged by her father, is enjoying being away from school, where she has flunked a couple of her exams. Raymond is unconcerned with her lack of interest in studying to retake her exams. He acts mostly oblivious to his responsibilities as a father and is more concerned with being his daughter’s “friend” and “companion.”