What does a paper town stand for metaphorically in the novel?

A paper town is fake.... an illusion. Metaphorically, it represents the way Margo feels inside, hollow and fake. Margot's determination to become something she isn't doesn;t make her happy, the more she attempts to present what she believes is the perfect image.... the unhappier she becomes.

“I didn’t really look down and think about how everything was made of paper. I looked down and thought about how I was made of paper. I was the flimsy-foldable person, not everyone else […] People love the idea of a paper girl. They always have. And the worst thing is that I loved it, too. I cultivated it, you know?”