4. Any advice for someone wanting to write a mystery for today's market.
My advice is DON'T. Never, ever, ever, ever write for today's market. Chances are good that today's market will change long before you're done your first draft. Maybe even before you're done your first chapter.
Instead, write something you're passionate about. Tell whatever story is in your heart and soul. Write the kind of mystery you love to read.
Writing for the market is like being a cubicle slave for a mega-corporation who doesn't know your name and doesn't care. And writing pays worse, with no benefits and no 401k. Writing for the market will never bring you job satisfaction.
If you hone your craft until you can communicate well, and if you believe wholeheartedly in the story you want to tell, you have all you need to produce a book people will want to read.
You're a writer. Be your own boss. Don't let anyone else try to tell you what to write. Writers and readers ought to shape the market, not vise versa.