I've experienced one crash trying to "read" a Spanish book. Second try didn't crashed and showed it was only available for English books. :-(
Kgul, it seems you can read language from ePub file, because you are able to right hyphenate (more or less).
Currently I have a Spanish book that hyphens wrong. It is a Amazon purchased one and DRM stripped (completely legal in Spain). I can take screenshots of it if you want, but perhaps this could be better:
http://www.4shared.com/android/8JaH1MnF
It's a legal download (it is a CoolReader 3 port to be run in andorid ebook reader (like Nook). It contains a hyphenation file (PDB or pattern) called "solsticio<blahblahblah>". It contains true Spanish hyphenation rules.
Perhaps this can be helpful to right hyphenate Marvin.
I have other two questions.
First one: When for iPhone/iPod? I've searched this thread and found nothing. A good thing could be do as iBooks: maintain books synchronized across phone and iPad.
Second: When installable dictionaries?
Currently Marvin is the best of the best, but I think that with those two things, it will be the best of the best of the best of the best of the... :-)
And one more thing: When searching for a word (I mean: open a book, tap and hold, select "Share", click "Web") it opens Safari, that means you have to return to Marvin closing Safari and reopening from screen or double tap start button and select from background... Could that be opened in a integrated window instead? Or offer user select what to open in configuration...