the more you read, self-confidence can be an enormous boost to your self-esteem. It could even aid in your career, as those who are well-read, well-spoken, and knowledgeable on a variety of topics tend to get promotions more quickly (and more often) than those with smaller vocabularies and lack of awareness of literature, scientific breakthroughs, and global events.
Reading books is also vital for learning new languages, as non-native speakers gain exposure to words used in context, which will ameliorate their own speaking and writing fluency.