The last time I read for fun was in elementary school. Since college I knew I must read more, but I never forced myself to build the habit. Then three years ago I spent time around my brother and a coworker who were avid readers. This "peer pressure" helped me get started.
Since I started, I've seen concrete improvements in vocabulary. I find myself using words I didn't know I knew. I question my choice of words more. And I understand coworkers a little better. Perhaps it is only personal style, but I've also become more aware of hyperbole in my speech and have begun to tone that down.
Specifically, books provide more density of information than I can pull together myself. I've also benefited heavily from reading books on tools I use daily. Contrary to being boring, a book on a topic with which I'm familiar has been a (often needed) break from books on topics with which I am unfamiliar. The former category might include books on CSS, Bash, Emacs, Python, Scheme, data modeling, Linux/FreeBSD system administration, mystery novels, and so on. The latter category might include books on Common Lisp, system architecture, the implementation of Linux/FreeBSD, behavioral psychology, management, stock/bond markets, the history of Argentina/Chile/South Korea/Japan, sci-fi novels, and so on.
Reading diversely exposes how little I know. And that can be depressing. But I'm fairly confident reading books is the fastest way to grow.
Tactically speaking, I started slowly with few books and the ones easiest for me to read. The first year I read two books, both technical. The second year I read nine books and was able to start branching out beyond technical books. Last year I read a much more diverse set of forty books. And this year I followed suit with forty-one so far (on track for fifty-five or so).
I keep track of books I'm reading and books I want to read in Goodreads. I particularly enjoy their reading challenge system that lets you know if you are on track to meet your reading goal for the year.