You write what you write. It is your theme, your subject. You write in your voice, and that is distinctly you.
Don't let anybody tell you that you need to write "like this" or "like that" to get a book published. Your voice is the completion of your experiences in your life.
I can speak from my own background, here. I wanted to have an agent, that was all I wanted. I wrote like "this author" and "that author" for so long, disregarding my own voice, racking up rejection after rejection.
I did myself a disservice.
Because when I wrote what I wanted to write (more on that in a minute) how I would want to read it, well, that's when I figured it all out.
Writing what you want to write.
This publishing game, it's hard, no question. Painful. So while you should of course know what's selling, you should BY NO MEANS write something merely because you think it'll sell. What if it doesn't? Then you've wasted months of your life on something you didn't really like.
But worse: what do you do if it does sell? What a tragedy! You're stuck writing stuff only like that until you're (hopefully) successful enough to step away and do something else. But you didn't really lust over your subject matter in the first place.
So...have you ever tried to write in another author's voice? How did that work for you?