This crossed my desk today:
The Army is pushing knowledge to the point of need by making e-Publications available for download to Soldiers’ mobile devices.
Doctrinal publications are accessible as Portable Document Formats (PDF) on personal computers and some mobile devices, but viewing them on mobile devices is less than optimal.
By the end of June, the Army will have converted many Army doctrinal publications to an EPUB format, making it easier to read on computer tablets and smart phones. Depending on the device’s sophistication, users can bookmark, highlight and insert notes on the publications.
The Army is in the process of converting their existing docs to Epub as well as to a rich ebook format I've never heard of before, E2Book.
It's described as having videos, animations and other embedded multimedia, but from what I see online this looks to be just a variant of iBooks. I don't have the specs so I can't tell you if it is simply iBooks by another name (perhaps a subset of iBooks with a restricted feature set?), but the one I found to download is reportedly only compatible with the iBooks app.
While it's all well and good that the Army is adopting a rich ebook format, I don't see a reason to move to Epub. I've found that nonfiction, particularly the dense and complex material that the Army publishes in its training docs, works best as a fixed layout format.
And since they're already producing PDF, I don't see a reason to replace them with Epub. Fixed layout Epub is significantly less useful and has fewer features than PDF, and it is also less widely supported.
But that hasn't slowed adoption significantly in the civilian world, or apparently in the military.