Write what you know?
Maybe the most commonly-offered, if not outright hackneyed, bit of advice on writing is, “write what you know.”
Screw that.
Write what you love.
Or at least what you like.
What do you want to read? More specifically, what sort of thing do you want to read that you’re not getting enough of?
Why not write that?
There’s a shipload of reasons to do that. First and foremost is: why make it hard on yourself? Or harder on yourself than necessary. Writing’s hard. Otherwise nobody’d be able to make any money at it. If you’re not writing what you love and loving what you write … why bother?
If it doesn’t entertain you, why should it entertain anyone else?
On a related subject - related to the bottom line, your prospect of actually getting anyone to pay to read what you write - if you’re not finding enough of the sort of thing you love to read, isn’t that a ripe old hint there’s an unfilled demand for it? Your demand for it ain’t being filled.
There you go: market research. Absolutely free.
Finally, on a realistic level, unless you’re selling regularly, there are no guarantees you’ll sell what you write - to say the least. So why not enjoy actually writing it as much as possible? At the end you’ll be assured of that much gratification at the very least.
There’s nothing wrong with “writing what you know,” surely. If it’s what you want, really want to write, wonderful. Otherwise - isn’t that what research is for?
I find I get the best results all the way around - personal satisfaction, sales, and fan approval - when I concentrate on writing the kind of thing I really want to read.
As always, your mileage may vary. Try it and see!