In science, some form of originality is absolutely crucial. I can't publish on a project unless I can convince an editor and the peer reviewers that I've either done something completely new, or that I've done some better than past researchers have done it. But, the writing world is, perhaps, a little more forgiving. Book publishers often chasetrends that allow writers to profit from copying the ideas of previous writers.
Honestly, I don't see anything wrong with that. For me, as long as I enjoy what I produce, I don't particularly care if it's original. At the same time, the thought of presenting the world in a way that no one else has ever seen it before is truly exciting. I'd love to hear that I'm doing something that no one else has done before.
What about you? Do you strive to be original? Do you think originality has to come from a conscious attempt to be so, or can writers stumble upon it? (Feel free to talk about yourselves and let us know how your work is different from what has come before it!)