Why hasn't it been remade?
Two great books by John Fowles, The Collector, 1965, and The Magus, 1968, were made into feature films with huge stars of the time. Can you name one other author who had two major films made of his work in the sixties, then you basically never hear from him or his films again? I find that very strange, I think there has to be a reason The Collector hasn't been remade but for the life of me, I can't figure why.
By the way, along the lines of casting a remake, I think it would be brilliant to bring back Terrance Stamp and show him still kidnapping girls, THAT would be a shocker!