A lot of books on Twitter

I went to a small bookshop in a supermarket and bought two booklets on Twitter. There are a lot of books on this micro-blogging service. I ended up buying five books or booklets. I have decided not to buy any more books on Twitter. http://j.mp/aN4X3Y

According to the description of Twitter, it is a "service for friends, family, and co–workers to communicate and stay connected through the exchange of quick, frequent messages." Its uniqueness may lie in the restriction as to the maximum number of 140 characters.