One of my favorite authors, Seth Godin, recently had an insightful post entitled "The Hard Part (One of Them)." I'll repeat it below for your reading enjoyment:
A guy asked his friend, the writer David Foster Wallace, "Say, Dave, how'd y'get t'be so dang smart?"
"I did the reading."
No one said the preparation part was fun, but yes, it's important. I wonder why we believe we can skip it and still be so dang smart.
I agree that reading can — and will — make you smarter. I would submit, however, that regardless of the voracity of your reading diet, it is vital for all of us — but most especially "smart" people — to regularly remind ourselves of how little of the sum total of human knowledge any of us has actually acquired (or, for that matter, can acquire).
One effective strategy for doing this is to create an "anti-library." It's purpose is to serve as a tangible reminder of how little we actually know.
If this fails, you can always just remind yourself of what Socrates once said, "I know nothing except the fact of my ignorance."