I was drawn to science fiction largely because of the radical (in a non-political sense) nature of the genre: here is a form of writing that starts from the premise that change is inevitable. Good or bad, it will happen, and the writer's job is to imagine plausible change and depict its possible consequences for people and their worlds. I've been lucky in being able to blend my own various interests into stories that catch readers' imaginations. Because, of course, science fiction, like any other fiction, is ultimately about the story, about the communication between writer and reader, the moment in which the reader is, fully, deeply, and willingly, part of the writer's world. Without the story, characters, plot, and setting, the writer has no right to ask for that participation; with it, the writer can take the reader into worlds s/he would never otherwise have considered.
I have always been most interested in the intersection of technology and society - of the hard and soft sciences - and I think that is reflected in my science fiction. I'm fascinated by technology and its developments - and I enjoy the challenge of playing by the rules of the genre, getting the science as "right" as possible - but I'm more interested in the effects of that technology on characters and imagined societies than in the development of some new machine or program. In other words, I tend to set my novels fifty years after a great breakthrough, and consider its aftereffects, rather than write the story of the discovery itself. My academic training (as a historian specializing in early modern Europe) meant that I was exposed to the work of the new group of social and cultural historians, from Michel Foucault to Natalie Zemon-Davis and Simon Schama, and the tools I learned for analyzing past cultures have proved invaluable for creating future ones. (In fact, my dissertation ended up being oddly similar to my science fiction, in that it was concerned with the effects of a technological change - the development of gunpowder weapons - and the unintended consequences of the model created to make use of it.)
Of course, since I'm a novelist rather than a futurist, all of this has to be expressed through plot and character. It's very hard to talk about the creative process without making it sound either stilted ("this developed from my interest in....") or mystical ("this character/place appeared...."), especially when both statements are always at least partially true. I tend to spend a great deal of time on the settings of my novels, cultural and social as well as physical, and to let both the plot and the characters grow organically from that process. I find that as I work out the details, particularly the ways that technology influences or upsets social norms (and vice versa), the inevitable contradictions that emerge are the most fruitful sources the characters and their stories. I enjoy the complexity and messiness of the real world, and believe that one of the real challenges of any fiction is to model that complexity without losing sight of the structure that makes a good novel.
It's also fairly obvious that I'm one of the few lesbians writing about queer characters whose science fiction is published by the so-called mainstream SF houses. I began writing about queer women first out of the usual impulse: I wanted to read about people who were "like me," and almost no one else was doing it. As I've gotten older, however, I've begun to realize that behind that superficially naive statement is something actually quite useful. Even in science fiction, there is a limited budget for novelty, both for the writer and for the reader; if one is creating something new in one part of the novel, other parts must of necessity be drawn from that which is familiar. In most of my novels, the technological and social changes are the new things, and, as a result, I draw on the people and culture in which I live to make up the balance. It's that culture, my own culture, people like me, that provides the emotional background of my novels. Certainly my fascination with masks, identity, and roles comes from living in a culture that is deeply concerned, seriously and in play, with just these issues.
Or, to boil things down to the basics, science fiction is one of the few genres that lets a writer consider very abstract ideas in human, messy, and concrete terms. And that very complexity is both an artistic delight and an intellectual necessity.
(There. I feel better now....)