Romeo and Juliet is a very old story. It was written by Shakespeare in the 1590s, and it's still widely loved and studied today. So, it's been around for hundreds of years.
Romeo was thought to be 16 and Juliet was 13. The contrast in their ages and the immaturity it implies plays a significant role in the story's tragic outcome.
Well, Romeo and Juliet is primarily known as a play. However, there are indeed novel adaptations based on the story. Different authors have put their own spins on it in novel format.