"The prolific novelist, who has penned something like 29 million words in his lifetime, has managed only four little missives thus far: two on the launch of his account (“no longer a virgin. Be gentle!”) and two on things he is reading and watching (Benjamin Percy’s “Red Moon,” and the French zombie drama “The Returned”). That lack of output hasn’t stopped @StephenKing from running up nearly 190,000 followers within its first days online and earning hundreds of retweets and replies to every little dribble of thought he allows out."
It isn't particularly surprising to me that a novelist like King would be struck mum by the fragmented format of Twitter, based as it on 140-character messages. Twitter is great for celebrities, political pundits, and business gurus, who think in buzzwords and catchphrases.
For novelists--who think in paragraphs and chapters--not so much.
If you're a novelist and reading this, I'm not trying to tell you that you shouldn't have a Twitter account. But you shouldn't view Twitter as all-important, or as a magic bullet for marketing your books.
The same goes for other social media platforms. Social media is an important part of marketing almost everything nowadays, so every author should probably have some sort of a social media presence.
That having been said, not every author has to file hourly dispatches on every social media platform. Moreover, some social media platforms are intrinsically of questionable benefit to authors (especially authors of fiction).
Take YouTube: Video-holics aren't necessarily voracious readers. Moreover, around 70% of YouTube's traffic now comes from outside the U.S., and (based on my experiences on YouTube) from outside the English-speaking world.
This isn't to say that people who reside outside the English-speaking world never read English-language novels; most certainly they do. But English-language books are significantly harder to market to readers whose first language is French, Japanese, Russian or Urdu. And as an author, devoting a lot of time and energy to courting these (potential) readers may not be the best use of your time, resources, and energy.
Which brings us back to Twitter: People who enjoy reading random 140-character fragments may or may not be interested in your 400-page novel, or your 500-page nonfiction book about the history of the Catholic Church during the Middle Ages.
For attracting those readers, a more book-like format--such as a blog or even a static web page--might be be far more effective.