Originally Posted by Nate the great
If you admit that there is incompatibility inside Epub then the Kindle's external incompatibility is less important.
And which Epub is the standard?
B&N, Kobo, and Apple each have their own fixed layout format; the content is not compatible. There's also Kobo's own internal format as well as Apple's implementation of Epub3 as well as the iBooks format.
So which is it?
Fixed layout is not ePub. It's something else. So we don't count that at all. B&N's ePub is box standard ePub just with a different flavor of DRM. Everyone else (except iBooks) uses standard Adobe Adept DRM with standard ePub. There are more readers, more programs, more apps that handle ePub. eBooks don't start and end with the USA. The world is into eBooks and ePub is the mot used reflowable format out there (at present).