it will be useful but you still need to listen and speak, practice language by reading to be able to write, and listening to be able to speak

Learning a language requires 4 language skills, reading, writing, speaking and listening. Language is used for learning and communication. So if you read books, that is a good element to incorporate!

Everyone has its own aims; if your aim is to become a writer in a (yet) foreign language, reading, reading and reading is the suggestion that good authors usually give to their pupils; my opinion (based upon how our mind works) is that the best you enjoy your learning path, the more you will learn.

Whilst reading books is very valuable, I suggest that you also build up your listening skills. Here's a link to help you http://www.italki.com/knowledge/page/IMPROVE%20YOUR%20ENGLISH%20LISTENING%20SKILLS.htm

Reading is a great way to learn. It's also a great way to structure a learning pair meeting. Pick a book you and a partner are interested in and read a section. Then discuss. Ask questions of one another. Then you will practice your reading and your speaking while enriching your life through a good book.