From Jan. 9 to Jan 11, Numbers Plus Four was free on Amazon as part of the KDP Select program. Before going free, the book averaged just one sale per month and was ranked around #500,000 in the Kindle Store. On the first day that it was free, about 100 people downloaded it. The book reached #1,800 on the "Free in Kindle Store" list and as high as #47 within the Short Stories category! (See screen shot below)
Interest faded quickly on the second and third days of the promotion. By the second day, the book dropped to about #2,400 on the "Free in Kindle Store" list and #90 within Short Stories. On the last day, Number Plus Four's ranking on the Free list dropped to #4,000 and it dropped off the top 100 list within the Short Stories category. During the three days, 127 people downloaded the book.
The ride up the rankings was fun on the first day, but it was disappointing to see that the momentum didn't maintain itself after that. More disappointing was that the downloads of Numbers Plus Four didn't boost sales of George and the Galactic Games at all. However, I did get another sale of Numbers Plus Four since the promotion ended, so maybe it'll sell more than one copy this month.
I have two more free promotion days to use between now and April. Based on my results this time, I think I will run two separate 1-day promotions. I want to try another day of the week and compare it to my Monday results. Then, depending on how well it does, decide when to run my last free promotion day.