Kindle Direct Publishing Select - Didn't work for me.
In a nutshell, this is how KDP Select works. You promise to publish your eBook exclusively through Amazon and they promise to make it worth your while. Specifically, you can have five promotional days each ninety day contract period. This may be in the form of Advertised Free days or a Countdown promotion. You can only do one of these during your contract period, so I can't speak to the Countdown promotion, since I chose the other.
The idea with the Free Promotion days is that so many people will download your book for free that you will top the Kindle Free charts and be able to brag about having a "Best Seller". By reaching that level, Kindle takes notice of you and starts promoting you book at other times, and you suddenly become famous. Well, that's how it has worked for others, and in the past. There are sites that say they will promote your book for free on the days you are running your promotion, though most won't guarantee they will run it unless you pay them $5 to $25 to push it.
The first time I ran this free promotion was just over a month after I released, "Flypaper Boy: Coming of Age". I used the two days after Thanksgiving. I had 180 people download it the first day and about 65 the second day. The highest I got on any list was Kindle/.../Adventure/Romance and I got to #5. On Kindle/..../Superhero I only got to #10. After that initial promotion I got three people downloading the book from the Kindle Online Lending Library. Initially you get nothing, but if they read more than 10% of the book, you get your regular royalty payment. I had one person buy at the regular price as well. All this within the week following the promotion.
The second time I ran the promotion was for three days. I got 40, 41 and 5 downloads for those three days, respectively. I had no followup sales. I ran this promotion the three days before Christmas.
I don't know if the days or time of year was bad to run these promotions. Since I only had ninety days to choose from, I went with what I thought would work for me.
So, as far as I can tell, every member of my extended family and the few friends I have have purchased my book, either as an eBook or Print on Demand (POD) through Create Space, and not a lot of others.
I will run one more KDP Select period and try the Kindle Countdown promotion as I'm releasing my next novel, "Shooting Stars: A Teenage Vampire Love Story from a Boy's Perspective". (Hopefully by the end of January.) We'll see how that works. Hopefully there will be carryover from the free promotion to generate awareness for the new book.