I believe books are excellent for acquiring many skills, including learning a new language. However emersion allows you to interact, to be corrected which prevents you from reinforcing mistakes in grammar/pronunciation, it also prevents you from procrastination. And for those who are auditory learners, emersion can help people overcome that learning curve.
It depends on the person I suppose.
Books, regardless of the topic, possess the potential to assist in the expansion of not only your vocabulary database, but also aids in developing your ability to understand different components of the English language. Grab a book and create a list of words that you stumble across that are unfamiliar and define them.
The more practice the better you will get. If you challenge your self you will get smarter. Books also contain many facts so there's that to. Reading helps increase ones vocabulary, one get better at spelling and it also helps one get better at reading and writing. Reading is very good for your brain.
One of the most important aspects of learning a language is reading. Put simply, a book is a manifestation of the author's coherent thought process. He or she uses the power of words to express ideas with utmost clarity. The hallmark of any good book is how understandable it is and how it can describe complex scenarios in a way that people understand. The reader of the book learns constantly from the subject matter of the book. He or she will not only understand what the author of a book intended, but also increases the size of his or her own vocabulary. This is very important since a very good vocabulary will help the person articulate his thoughts more clearly. This directly contributes to the person's English language skills. However, reading is not enough. Writing and speaking play crucial roles since they put the person's English abilities to the test. Reading, speaking and writing combined together provide a synergistic effect in the person's comprehension and familiarity with the language.
Reading is very good for your English, there are three level of reading. The first level is reading silently, you only can understand what the book means; the second level is reading out loud, by reading out loud, your can understand the story and figure out the words you don't know; and the highest level is after reading it, write it in your own language, so you can highly understand the story.