Isolated in a remote villa on a little Atlantic island, the three participants certainly do a lot of talking. But that's what the French enjoy in life as in film, particularly here when there's a high charge of sexual tension and sibling rivalry.
It can certainly be seen as a feminist tract. The man is studying to be a librarian, rides a bicycle, and wears a voluminous waterproof cape. The two sisters let him do the cooking and seduce him in turn. While one only wants his sperm, the other does have hopes of a relationship. Which could be why she wears glasses, in order to look a librarian's mate, but then she comes to his bachelor bedroom in revealing nightdress and black stockings .....
Artificial as story and characters may be, the director treats them both seriously and satirically. Yet what do their little love problems matter in a huge and complex world? Why do they go on about organic food and exercise while smoking almost continuously and putting away vast amounts of alcohol? And why do the girls play their father's old Boby Lapointe vinyls? To some they may seem witty period pieces, but to most young people born in and since the 1990s I imagine they must sound like bleeps from an alien planet.
PS A slightly ridiculous young Frenchman becoming the object of attention for two very different sisters in an isolated house on the Atlantic coast was the theme of "Les Deux Anglaises et le Continent" long ago in 1971 - too long ago to influence the present film?