I've been trying to find the "Moon Rocks" example on iTunes U but, so far, have failed to locate it.  Any cues will be appreciated.

Yes, Calibre has a usable ePub reader built-in plus it makes a mighty fine OPDS server if you have a fixed IP and access through your institution's firewall. You can do OPDS via DropBox, too, but the DropBox solutions I've seen so far are not as good as what Calibre can do. Another WebKit option is Ibis Reader from Threepress Consulting which is constantly being improved. Still, iBooks is my preferred test bench since it supports, audio, video and Javascript to some as yet unknown degree.

Regarding the need for an ePub reader comparable to iBooks on MacOS X, I second that emotion. Currently, ePub is the only media type supported by the iTunes.app and iTunes U that cannot be "played" directly or indirectly (a la PDF) via the iTunes.app. That needs to change. In the interim, one must sync to iBooks on iOS in order to get good feedback on one's writing. Perhaps iCloud will provide some relief but I really think that nothing less than an app will do. My MO requires rapid switching between the views of content creator and content consumer. There is also the EPUBReader plug-in for Firefox, calibre and the Sigil and Adobe Digital Editions apps. Those alternatives don't yet support audio, video, etc. but the finalization of EPUB 3 should change that or at least I hope that it will.

Thanks so much for this. It's just what I needed.

@gerald1248, That's great and I hope the others involved do likewise. Please post a link when you do. I looked around at: http://itunes.apple.com/WebObjects/DZR.woa/wa/viewTagged?id=380206132&tag=OpenLearn ... but there's so much there I fear that I may be missing it or in the wrong venue altogether.