A young woman is abducted by a man who's grown obsessed with her in the previous months (or years), and wants her to fall in love with him too. But once she's in his power, he is at a loss what to do with her ..
The story is told from his point of view, and then hers, which provides the reader with a distorted yet deeply interesting account of the same events. John Fowles's observations are very cruel but also very, very true - people like Frederick, his hero, can never fit in. They can only use violence to serve their own purposes - but even that does not always work - as you cannot force somebody's mind .. in the story, the woman never acts as he expects or would like her to, and it's very obvious she doesn't belong to his world, and never will.
Which can only lead to tragedy, even if people don't want things to end this way.
The plot of the Collector reminds me of stories by Edogawa Ranpo or Ernesto Sabato - I remember the former wrote a weird novel about a masseur using women's bodies to fulfill his desire for Perfect Beauty.
That said, Fowles mostly reminds me of the best writers/analyzers of the human mind like Kellerman or Mac Ewan.
But he's also a great writer of his own right .. I first read the Collector more than 10 years ago, when I only was in my early teens ... and it's still as good as it was at the time.