Agents are looking for the next big thing. Publishers are looking for great voices. All are looking for the next story that moves them, speaks to them, changes their way of thinking for those several hours they dive into the book.
You want to be the one person that drives them to think about your novel for days.
However, you can't be too unique. You have to borrow a story and give it a fresh take. No, I'm not talking about plagiarizing. That's wrong (obviously).
What I'm talking about is the unique take on an old idea.
Stephanie Meyer took the old idea of a vampire and turned them into 'vegetarians' and had them live kindly among humans. That's an entirely new take on the old vampires that suck your blood.
How about J.K. Rowling's wonderful tale, Harry Potter? Wizards and witches are used to being burned at the stake, using their brooms only at night. Cackling and warts? Nah, none of the above... they attend school regularly, learn how to properly ride brooms, and laughter is just like any child. See what I mean? A new take on an old idea.
See? Something Borrowed. It doesn't just apply to weddings.