If readers do not know your book exists, they can neither purchase it nor read it. Thus, marketing becomes part of the job of a self-published or indie author. Even traditionally published authors must work at marketing their books in today's publishing world.
Advertising is expensive and while it can be very effective, you need to know what you are doing in order to obtain a return on your money. It is also difficult to determine how effective your advertising dollars have been spent. Many authors who self-published have spent large sums of money to no avail.
Since most of authors who self-publish are on shoestring budgets, taking advantage of marketing tools that are free or low cost is an approach worth examining.
While KDP Select free ebook marketing is not what it used to be, it is an effective approach if readers know your book is available for free. The key is to get the word out and not just rely on readers who go to Amazon alone to search for your book.
Using your author platform tools (blog, social media or newsletter), you can make readers who are already fans aware of your promotion.
The goal though, is to get your book in front of as many NEW readers as possible. This is where ebook promotion sites can be a big help.
There are dozens of ebook promotion sites on the internet, requiring you to be careful about which ones you select to use for spreading the word about your book promotion. Time is valuable and you will want to only use sites that can truly get the word about your book promotion in front of as many potential readers as possible.
To make sure the sites you select will do the job, use Alexa to check their traffic. Use sites that pull good numbers. It is a simple game of math. The more visitors a site has, the more likely readers will see your promotion.
If you are willing to spend money, the best pay site on the internet is BookBub. Be forewarned, this site is choosey and your book may not make the cut for one to be listed. This is a big part of why the readers who visit this site do so. The books listed are better than average, must be free or deeply discounted and the promotion must be a limited time only offer. With over 1 million subscribers, you can see the value of getting your promotion listed.
Frugal Freebies deals with more than books but does have a good listing of free ebooks. It's broader coverage of free items increases the number of visitors to the site.
Pixel of Ink deals with free and bargain Kindle books and allows readers to search by category or genre.
There are plenty of sites to choose from. In addition to doing an Alexa check, check the sites for their social media numbers, size of their newsletter list, etc.
One final suggestion. Make sure you check the timelines involved in dealing with each site. Some require considerable advance notice before listing your promotion. You don't want to have your promotion not listed because you did not give sufficient notice to the site.