The thing that makes social media special has nothing to do
directly with promoting an author or their book. Social media (in this sense) is about the connection made between authors and authors, between authors and readers, and between readers and readers. An author whose online social presence becomes a powerful promotional tool did so because their connection between these different groups is strong and important to the author. Authors who have blogs or Twitter accounts or Facebook accounts for the one and only purpose to promote their book don't really succeed, or at least, won't succeed in the way they want to.
The thing is, you have to love connecting with your audience for social media to work. And you shouldn't try to do everything. Who has the time? Pick what you enjoy doing - blogging, Tweeting, Tumblring, Facebooking, whatever, and do that
very well .
I suspect it depends on the genre and audience, but what it comes down to is this- readers love getting more about the authors and books they love and the blooming of social media has facilitated this. Readers can find interviews, extra content, insights into the story creation, into the characters, and into the world building. It has created a way for book readers to review and recommend, for authors to recommend, and for special events like live talks and interviews that would otherwise be impossible for readers to see if the author never comes to their city.
For a marketing aspect, social media allows people to keep talking about you and your book. If you stay active, then so does your name. You post good material, people continue to talk about you.
What I believe about every person involved in social media, whether they are a writer or a would be writer or a book blogger, a person who really loves their garden or posting pictures of their cats, is this - you have to love doing it for its own value. You cannot look down your nose or find what you are doing to be a waste of time because your audience will know and they won't appreciate it. You cannot expect a certain promotional outcome from everything you blog about or everything you tweet about. The promotion and marketing happen as a result of you being engaging, interesting, and valuable to your readers.
If you're not going to love connecting with your readers, whether you have 10 or 100 or 1000 followers, then I think you shouldn't try. As a reader, when I find an author's blog who is clearly only selling at me and not actually invested in their blog presence, it negatively impacts the way I see them. Granted, part of that is because I am so invested in social media, but I think most people don't like being sold at.
Take, for example, author Jackson Pearce. She has a great blog anyway, but last year she posted this video she made:
http://www.youtube.com/watch?v=-ZUA7-y2tUQ It's called Writer's Blok and is a parody of a more popular song but it is such a great, funny video and
everyone was posting about it when it came out. A year later and I still see it referenced on blogs and Tweets (and see, I'm referencing it here!) The word of mouth value on that video was ridiculous. And while it no doubt helped her when her book, Sisters Red, released last year, you can tell she didn't do it specifically for promotional reasons. She makes lots of fun videos and she blogs regularly. She does weekly live shows with her fans. She loves the connection social media provides and it shows.