Both of these books are now available free for Kindle Unlimited and Prime subscribers
Before you get too excited, Kindle’s new KDP format is a PDF wrapped in proprietary code for the Kindle. The books appear to read fine in a Fire or one of the Kindle apps. All I’ve seen is the previewer in the KDP upload page.
Producing the book is very fast. Download the free Kindle Textbook Creator from Amazon. Then you upload your PDF into the app. and follow the instructions on the right side of the window. The process is very fast on my iMac. After you have packaged the book, you open your KDP account and upload the book normally as a new book. The processing time is seen when KDP processes the KDF file into a Kindle book. As usual, they are not telling what they are doing.
The resulting book is simply available as a Kindle book, but it’s only readable on a Fire or in one of the Kindle apps for Mac, PC, iOS, or Android. MY assumption is that it is really not readable on a smartphone—even an iPhone 6 Plus. I suspect the type will be too small for a phablet.