@Tex2002ans: IMHO, the doppeltext version that shows both English and German texts on the same page looks a bit confusing.
I prefer simple interlinked paragraphs. For an example, see my simple French-English version of
The Three Musketeers.
It also has the advantage that this kind of output can be easily generated from a two column spreadsheet with a script or macro.
BTW, doppeltext has also created a layout
optimized for ePub3 that shows each translation as popup on the same page. IMHO, this is the best format for iBooks and other ePub3 readers.