I bought all 6 of the ones on sale. I was able to use these 3 on my Kindle 4 NT e-ink device, as well as the Cloud Reader. I wouldn't necessarily
recommend reading them on an e-ink device, but it was possible.
It would only allow my to use the other 3 on my Android tablet - no PC, no Cloud, no TouchPad.
I'll have to look into using the tools with my Kindle instead of with Kindle for PC.