Once you have your three genre categories and some initial ideas, it’s time to do some more in-depth research back at home to see if you can come up with a list of other recent books in each of those same categories that have something in common with your proposed title. … Most editors want books published in the last three years, four years at the very outside. Anything published more than a few years ago does not reflect current market trends or sales demographics.

Tilar J Mazzeo, How to Write a Bestseller, loc. 333