Summary of ad results for 99c sales

When I did my 99c Countdown Deal of Yseult two months ago, I promised to do a summary post after this round of promos was over. Last week, the third week-long promo ended, and now I have put together my results to share with you, along with some conclusions about running a 99c sale. I did not apply for a Bookbub ad for any of these promos, since part of my motivation in testing ad sites like this is to find alternatives to Bookbub. I have had Bookbub ads before, and I know that they are effe...