and have you looked at our German forum?
https://www.mobileread.com/forums/forumdisplay.php?f=159
Here is a site with free books also, which has many books in German.'
http://manybooks.net/language.php?code=de
And this one
http://www.feedbooks.com/userbooks/t...de&range=month
All books are in public domain, which means you won't find the best sellers, but you will find great reading, and by independent authors as well.
Enjoy.