The best way to become a better writer is to read more and not just about a single subject matter. Why? Reading is the best way to generate new ideas. Every person has a different perspective on life. This comes from different experiences, cultural ideas, values, etc. You know things I don’t know. You can make connections I can’t make. By reading, you are allowing these unique connections to flourish, which can make you a better writer.
Thanks to Luca for the reference.