I watch the Amazon rank of my books to get a measure of what’s going on. Since I’m not the publisher of my books, I don’t have access to the underlying raw data from all of the different places where my books are sold. But watching the Amazon rank gives me some indication of what’s going on.

The reasons why the rank changes are pretty inscrutable. When people buy copies via Amazon you see a big bump. When nobody’s buying, it declines. But it sometimes goes up and down small amounts for other undetermined reasons: Maybe people searching for it? Or making searches in which it appears? Who knows?

When Better Angels: Tour de Force came out, we marked the original Better Angels short story free everywhere. It’s the first story in Tour de Force and you can see it for free as part of the digital preview anyway. But it turns out that you can’t mark Kindle books free. Amazon won’t let you. If Amazon sees you’re giving a book away elsewhere, however, it will sometimes mark the Kindle book for free too. (This happened with The Third Time’s the Charm, which is still free everywhere, including at Amazon.)

When a book is free, its rank seemingly goes way, way up. That’s not too surprising, I suppose. When it was marked free, it went from ~3M to about ~50K and then would bounce around there. It would sometimes spike up to 1500 or so and then drift back down. I noticed it spiked up the other day and then, when I checked again, it had dropped down to 3.5M. “Huh?” I thought. So I went to look at the product page and noticed that it wasn’t free anymore.

It’s still free elsewhere. I checked at Smashwords and Kobo anyway. Weird. It’s impossible to know why Amazon does anything they do — other than that one can reliably predict they’re shoving their blood funnel into anything that smells like money.