Well, an 'earth day novel' could cover a wide range of topics. It might be about a future dystopia where the Earth has been severely damaged due to human negligence, and the characters are on a quest to restore it. Or it could be a heart - warming story set in a community that comes together on Earth Day to plant trees, clean up beaches, and in the process, they learn valuable lessons about the environment and each other.
Since there are numerous novels that could potentially be called an 'earth day novel', it's difficult to say without more context. It might be a story that focuses on the beauty of the Earth and the need to preserve it. For example, it could tell the story of a group of people who fight against environmental destruction, highlighting the importance of Earth Day as a reminder to take care of our planet.