After I offered my book for free in the Amazon KDP select program and it was downloaded by 13,700 readers (you can read about this in my next BLOG), the same book sold really well for another week. The reason was a higher place on the Amazon sales ranking.
In short: the more books you sell, the more Amazon will help you to sell more. The higher on the ranking list you are, easier it will be. It should be your goal to reach the list of 100 bestsellers .
- Understanding Amazon Sales Rank
- Amazon Author Rankings and Who They Actually Benefit
- Amazon & The Importance of Popularity
So it should be your goal to create a buzz on the social networks even before you offer a book for free. During the promotion, frequently send out the information about the book being free. And after the promotion, post about how successfully the book is selling. If you succeed, Amazon will help you by ranking you higher and the book will really start selling.
A combination of free promotion, Twitter and Amazon ranking can be a very powerful promotional weapon.