Working on two books at once

I've never been the type of writer who can work on more than one book at once. When I'm writing a novel, I'm usually so focused on it that I can't think of other novels for fear that it will pollute the one I'm working on. That changed recently when I stopped working on the YA fantasy series that occupied the first half of this year.

Last month, I started a new novel outside the YA genre. It's a thriller because thrillers are my second favorite genre after YA. I spent a couple of weeks coming...