From the time a person learns how to read, he should keep on reading for the rest of his life. Reading books engages the brain, and the action itself keeps the mind sharp. But there is also information in books. The best way to transfer that information to yourself is by reading it.
Vocabulary
When you read books by great authors, it's very likely you'll come across words you've never seen before. This doesn't mean you should feel stupid but that you should take pleasure in this opportunity to deepen your vocabulary. Always have a dictionary nearby while you read. The more you read, the more you'll develop your own vocabulary.
Be sure you're changing your reading selections from time to time. If you read only sports books, you will miss out on a lot of vocabulary that you could be finding in historical biographies or classic literature.
Entertainment
A myth about reading books is that it's a boring activity. This is true only if you're either impatient or unwilling. For anyone willing to take the time to read, it can be one of the cheapest and most satisfying forms of entertainment. Almost everyone has seen the movie "Jurassic Park," but the book is just as exciting and fascinating in its own way. If you need a half-step between visual and written entertainment, pick up a good graphic novel. "The Watchmen" is one of the most popular, and since it tells such an engaging story it may be your gateway into a book-reading routine.
Education
Anybody can go on the Internet to look for information, but the sources are still not as reliable as a book. A trip to the library or bookstore is like a patient man's web-surf. Hours of information can be accessed from books, and since it requires more time for a reader to ingest it when it's coming from a book, it's more likely to stick in the memory.
History, science, philosophy, comedy and relationships are all topics that books cover in detail. If you want to learn about something specific or just anything at all, reading a book will continue your education in the school of life like nothing else.