Should I research the publishing market before I start writing?
Have some vague idea of what the market has been doing for say ten years might be wise, but the publishing market does move on. If you try to write for the market, you'll find yourself becoming unstuck, because by the time your book is published, that market that you were trying to copy has changed. They tend to change on the basis of a sensational type of novel that sells many copies. But the next sensation will have nothing in common with that first one.