Why do I write? The most basic answer, I suppose, is that I can't not do it. I've been telling stories on paper, first to myself and then to other people, for as long as I've been literate.
Being able to do it well enough to make a living at it has advantages, no doubt. I set my own hours. I eat when I'm hungry and sleep when I'm sleepy. I work on projects that I want to work on, when I want to work on them. Only one person—my editor—stands between me and my audience. For someone who spent 11½ years in the midst of an educational bureaucracy, if that's not heaven, you can sure see it from there.
The downside to this is that I have a much tougher boss now than any other I've ever worked for. Sitting at my desk and doing nothing is not an option any more. Well, it is, but not if I feel like eating and keeping a roof over my head. Not everyone is able to work without somebody else giving orders—generally, in a loud, unpleasant voice. I'm lucky enough to manage that: usually by internalizing the loud, unpleasant voice.
Very often, when I'm working, I'm interested in finding out what happens next, because sometimes I don't know in advance. I'm not a writer who plans everything before it goes down on paper. I usually know in broad terms where I'm going, but not how I'll get there. And getting there, as in so many things, is much of the fun.
I also want my readers to have a good time on the ride. I'd better. If someone with book or story in hand doesn't care to keep turning pages, all else fails. If, after that, I manage to spark some thought, too, so much the better. But entertainment, of necessity, comes first.
I'm one of those people for whom the line between research as work and research as fun blurs. I'm a historian by training and a bookworm by disposition. Writing alternate history, fantasy, and historical fiction is an ideal excuse to fatten up my library and write off the money it costs on my taxes. Reading seems as likely as anything else to spark ideas in me. You never know what you'll find till you look. The more places you look, and the more widely, the better your chances become.
In pursuit of one writing project or another, I've been to Hawaii, to the Jet Propulsion Laboratory for Voyager's flybys of Uranus and Neptune, to Yellowstone, and to Stonehenge. I've handled an AK-47 (well, a Chinese copy). I've flown in and briefly piloted a Goodyear blimp.
I could go on—but my kindly editor here would just abridge me if I did. So I'll just close by saying that, if you're lucky enough to be able to do it, writing beats the hell out of working for a living.
The War That Came Early: The Big Switch