@DaleDe: I've got a link for your locked
Multilingual eBook topic:
Aglona Reader free Android/Windows app for parallel books.
Also, it might be helpful to investigate which readers/apps actually support books that don't use the Latin alphabet. Based on my limited research, the best options are Kindles, PocketBooks and Kobos:
Kindle readers/apps: both apps and readers come with
code2000 as a universal fallback font and can display most languages covered by the the Unicode 5.2 standard.
Amazon also bundled some CJK and Indic fonts with all current models and apps and 2 Arabic fonts with the current iOS and Android apps.
PocketBook: PocketBook readers support Greek, Hebrew and Arabic, many Eastern-European languages (e.g. Russian, Ukrainian, Kazakh and Georgian) and CJK.
Kobo: Kobos come with an epub3-compatible rendering engine and
should be able to display all non-Latin alphabets in kepub books properly, if a suitable font is embedded or installed on the device. Kobos also have built-in support for Japanese.