A number of websites will promote you book for free, usually by posting a thumbnail of the cover and a brief blurb about it. Some of these sites also let you post press releases about your book or to write a promotion for your book that they’ll tweet.
Given that these websites don’t bring in as many visitors as Amazon.com or Goodreads and so don’t sit very high on search engine rankings, taking the time to post your book on them may seem like a wasted effort. Still, many of these sites – usually geared at specific genres of independently published books or for ebooks – often boast thousands of readers. You never know what potentially interested reader will spot your book on one of those sites.
In any case, the real long-term benefit of these sites is when they link to your personal blog or website that promotes your book. This raises the ranking of your blog or website, which increases the chances that over time someone looking for a book just like you’ve written will stumble across it via a search engine.