
Speculation is that the addition of ePub support to Edge browser (still only in preview build I think?) has paved the way for this.
http://www.pcworld.com/article/31585...le-ebooks.html
http://www.techradar.com/news/window...-leak-suggests
Wonder if Edge offers (or will offer) offline mode for this content (as Kindle Cloud Reader does). I am not willing to install preview build of Windows 10 to find out, however. I just removed preview build from my Windows 10 Phone as half the apps I wanted to use stopped working...