Definitely one of my favorites, too. There's an elegiac quality to it that I haven't quite seen in any other novel.

I have a number of quotations jotted down from it, but since this a tech site I'll restrict myself to sharing this one that I sometimes think of when dealing with a recalcitrant machine or mysterious bug:

        "That contraption--listen, Brother, they claim it thinks. I didn't
    believe it at first. Thought, implying rational principle, implying
    soul. Can the principle of a 'thinking machine'--man-made--be a rational
    soul? Blah! It seemed a thoroughly pagan notion at first. But do you know
    what?"
        "Father?"
        "Nothing could be that perverse without premeditation! It must think!
    It knows good and evil I tell you, and it chose the later."