After reading yesterday that Kindle sales are actually exceeding traditional book sales on Amazon, I set out to figure out how to get "Through the Open Window" available for Kindle. It was actually extremely easy. Go to https://dtp.amazon.com/mn/signin and answer a few simple questions and upload your file. The only thing I had trouble with was uploading the cover. The preview image that they offer was extremely distorted and I had no idea if it would appear correctly (It does). My book was live in 24 hours. It is available for only $2.99 (the lowest price available - of which I get to keep 70%) The only thing I couldn't figure out was how to have the Kindle version show up on as "another format" on the traditional book page.
This is for the Kindle edition:
This is for the traditional book: