To quote John Gardner out of his book On Becoming A Novelist (Harper & Rowe, 1983):
As for the quality of strangeness, it is hard to know what can be said. There can be no great art, according to the poet Coleridge, without a certain strangeness. Most readers will recognise at once that he's right. There come moments in every great novel when we are startled by some development that is at once perfectly fitting and completely unexpected - (...) Strangeness is the one quality in fiction which cannot be faked.