Your new novel may have3,000-year-old competition
14. It’s important to investigate the competition before you start publishing. Pick something you know about, which you can contribute something new about, which lots of people care about, and which lots of people have not already written about. If there are other books on the same topic (and there probably are), make sure you have something important to add so your book can be better than the others.
From my 1001 Powerful Pieces of Author Advice.