When I put together the original pay-per-click advertising campaign I did on Facebook, I went to a lot of trouble to target people with likes I thought would fit well with Trang--social science-fiction, Babylon 5, etc.
But yesterday, when I first noticed that no one was clicking on the ad, and before I figured out that the ad simply wasn't being displayed, I though the problem might be that these people didn't read e-books. So I quickly threw up an identical campaign that was aimed solely at Kindle users. (Again: Beat that, dead-tree advertising!)
Well! Today both ads are indeed being displayed, but still none of sci-fi crowd is clicking on the ad. The Kindle folks, however, are clicking. (And they appear to be actually grabbing free copies--Trang is now #3 in science fiction:series, which kind of cracks me up. Can I claim it's a bestseller now?)
So, definitely ads for the next set of KDP Select free days will be aimed at Kindle users. Trang is available as a paper book, so I'm gonna keep things going with the sci-fi crowd, since it can't hurt (and if they don't click, it doesn't cost me a dime--seriously, pay-per-click ads are kind of like e-books, where it's more trouble to take them down than to leave them up). But it looks like it'll be well worth it to have specific campaigns for each kind of e-reader user--Kindle, Nook, Kobo, whatever.
The reason I didn't initially market to Kindle users is that marketing sci-fi to a general audience often isn't very productive. But with pay-per-click, as long as I am very up-front about the kind of book it is (and I'm using the "clever return to the social sci-fi of yesteryear" line), the audience seems to self-select. Since (unlike with display ads) I don't pay for those who don't click, it doesn't matter if only 1% or 0.1% or 0.01% or 0.001% of the people who see the ad are interested.