Originally Posted by HarryT
Yes - add a "double extension": ".epub.kepub". That should make it use the new engine.
Neat. Most things seem to work pretty well. Multi-column layout. Embeded fonts. Right-to-left, including 'reversed' page turning (tried with Arabic and everything looked nice). Even MathML seems to be mostly working. Also allows for zooming/panning of full-screen images which the regular engine doesn't.
Need to find a doc' with proper footnotes (either end-of-page or pop-up), which is the ePub3 feature I'm really looking forward to, to see if that works...
Wonder what regressions there are that keep them from using this new engine for all books.
Edit -- indeed it does support popup footnotes! at least in very basic form.