There are some other German ebook stores which would be interesting to see under GetBooks as they often offer high discounts on ebooks:
www.thalia.de
www.weltbild.de
www.hugendubel.de
www.buecher.de
www.pageplace.de/de/bucher.html
Good ebook store in general:
http://www.ciando.com
Perhaps you will find the time to implement one or the other...
Thanks in Advance