Please see the "notes" section of this U.S. paperback. From the front cover scan, enlarged, it's possible to read the mention of the original title in the small print under "The Day After Tomorrow".
This is quite a good story, although it might currently be viewed as politically incorrect in parts. I hope that the German translator captured, relished, and transferred Heinlein's excitement and philosophy for the benefit of German readers. The German cover art is certainly better and more interesting than the U.S. version linked above.
The symbols on the spine are from The Phaistos Disc, one side of which is illustrated on the front cover. Additional information about The Phaistos Disc, which has been jestingly referred to as the world's first compact disc single, can be found in this PDF document.