fireland, if you purchased the universal version once, you can download it as often as you want - especially at this time while it's being *free*.
So, first of all, do a backup in your current Marvin installation:
http://blog.marvinapp.com/post/64407495557
Next, delete Marvin. (Yes, do it!)
Then either search for "Marvin - eBook reader for epub" in the AppStore or follow this link to it:
https://itunes.apple.com/us/app/marv...1209?ls=1&mt=8
Install it.
Restore your backup:
http://blog.marvinapp.com/post/64407495557
-> Read happily ever after.