PressBooks does a reasonable job of importing ePub, so that ePub can be used as a portable format for open text books. But, of course, there are limits.
I have been really impressed with PressBooks, the extension to WordPress for authoring eBooks. Like WordPress it is available as a hosted service from PressBooks.com and to host yourself from PressBooks.org. I have been using the latter for a few months. It looks like a great way of authoring, hosting, using, and distributing open books. Reports like this from Steel Wagstaff about Publishing Open Textbooks at UW-Madison really show the possibilities for education that open up if you do that. There you can read what work Steel and others have been doing around PressBooks for authoring open textbooks, with interaction (using hypothe.is, and h5p), connections to their VLE (LTI), and responsible learning analytics (xAPI).
PressBooks also supports replication of content from one PressBook install to another, which is great, but what is even greater is support of import from other content creation systems. We’re not wanting monoculture here.
Open text books are, of course, a type of Open Educational Resource, and so when thinking about PressBooks as a platform for open text books you’re also thinking about PressBooks and OER. So what aspects of text-books-as-OER does PressBooks support? What aspects should it support?