I just did a cover reveal for the fourth novella in my "Deeds of the Ariane" fantasy series:
So after Tina Folsom visited my local chapter and mentioned that she made the first books in her series free in order to drive sales to the rest of the series, I decided to try it. I had nothing to lose, so why not?
It took a while, but after Lark's Quest: The Search had been free on Barnes & Noble and iTunes for a while, Amazon.com price-matched it to $0.
So did it work? Well, the cover above is the answer. The fourth book is now a *much* higher priority for me, and will get completed this year, since the first three are now selling almost as well as my other series.
I'm not sure making a book free would be worth it if it's a stand-alone. That used to work (I did it with my first book in the KDP Select program last year, and it drove the book up on the bestseller lists for a while last spring). Amazon seems to have changed the way they calculate free "sales", so making a book temporarily free doesn't seem to have as much impact long-term as it used to.
But if you have a series, and would like to raise visibility, making the first one free for a long time (not the KDP Select 1-5 day limit, but weeks or months at a time) seems to work, at least for me.
So that's my little tip for the day--sometimes giving something away can make potential readers aware of you, and then, if you're lucky, they'll check out the rest of your books.
Happy writing, all.