Don’t get caught up in the game of comparing your idea with every other author out there. It’s not about their take it’s about yours. What makes your murder mystery an intriguing puzzle the reader won’t want to put down? What makes your romantic couple one that readers will be shipping long after they finish the book?
You have a unique spin that sets you apart from the pack. All you need to do is figure out what it is.
Write like no one is reading.