By Author, Derek Haines on Just Publishing Advice site:
Twitter has become the go to social media platform for self-published authors over the years. Perhaps this happened because both self-publishing and Twitter were launched at roughly the same time, or the immediacy and ability to blatantly flog a product on Twitter was a better fit than other platforms that constrain or demand payment for product plugging.
For whatever reason, Twitter has definitely become seen as the essential platform for self-published authors, but is it effective in delivering what authors want? Book sales. Does Twitter sell ebooks?