In each of the other books, the character basically finds out that there is more to their world than they thought. Harry discovers the wizarding world, Bella discovers vampires and werewolves, Percy finds out that Greek "mythology" is true, and Clary discovers the whole Shadowhunters thing. So whats the significance of this? I think what it boils down to is that it gives people the feeling that this fictional world could coincide with ours, and that helps them to accept and relate to the story and characters more, because atleast they share/ shared part of their world with us. Plus (but I'm not entirely sure on this), I think people like to think " What if? ". What if theres more to our world than we think there is? What if there are demigods, wizards, vampires, etc out there?
While this is all good usefull information, I was pretty sure there had to be more. And then i read this. Needless to say, I think she pretty much nailed it. ( I also think Im kinda an idiot for not realizing it earlier...). All of the "big" stories out there were new. DIFFERENT. They defined the genre/ topic that they wrote about. People think " Ooh, Twilight did very good, I think I'll write about vampires now." and think that thats their ticket to going big, rewriting something thats already been there, done that. But its not. ( Even though it does work sometimes, just not as well...). We dont want to revisit Hogwarts with a different Chosen One, we want to go somewhere new, someplace different that no ones showed us yet.
So now its your job to find that place and take us there.