There are some French and German books on Project Gutenberg.
Amazon won't let me buy ebooks from Amazon.fr (
list of bestsellers: right hand column is free ones), but I look there to find the free ones, then search on the UK site to download them.
I think most of the French ebooks can be bought from the UK site, but only get them from Amazon if I can't get them anywhere else, because I don't have a Kindle. I haven't tried any German books, but I would imagine the situation would be similar.