I don't know. I have asked people everywhere this same question and interrupted a kind gentleman in London during his meal once to ask why he was reading the book he was reading. We talked about Ian McEwan, even though at the time the most important book for me was Baudelaire's prose poems.
I don't think I'm looking for anything specific when I read. I do want to be pulled in and stirred and imagery has to be created a little unusually, perhaps. I don't need much. I need a character or a premise glued with a feeling, a sentence that sticks out like a broken bone coming up through the flesh, a paragraph that has musical importance. I don't want to get into syntax but I want the author's aesthetic unity when I read. My head is open to being played with. My heart, a little more out of reach, but wanting it, wanting contact. Yet no one appreciates suitors who try too hard.
But I think that this is hard enough. This is enough.