De regels van drie (The Rules of Three) was recently published in German:
Opi Kas, die Zimtziegen und ich - Aladin Verlag, 2015. Translation Meike Blatnik. Illustrations Joëlle Tourlonias.
This month the book became winner of a Luchs. Every month Radio Bremen and quality newspaper Die Zeit award a Luchs to a newly published book. The twelve winners are nominated for Luchs of the Year.
The radio broadcast about Opi Kas, die Zimtziegen und ich is available online.
And more here.