Book promo sites can be an extremely useful way to reach new readers. Essentially, authors discount the price of their book for a limited time and pay a third-party to publicize this offer in an email blast. This strategy is made more effective by using multiple promo sites at the same time to publicize an offer, called promo stacking.
Of course, you will need to be able to control your book’s pricing. Here are instructions for Draft2Digital, Kobo, Google Play and Amazon: Schedule book price promotions [Draft2Digital, Amazon KDP, Kobo Writing Life, Google Play Books]
Promotion type – free or discount
You can promote a book for free or discount it (99¢ is probably the best discount price). Free promos are great for getting some intial reviews and generating buzz. Discounts make more sense for a more established book. Whatever strategy you choose, some of the best promo sites are The Fussy Librarian and Written Word Media, which has the Freebooksy service for free promos and Bargainbooksy for discount offers.