Originally Posted by jocampo
But I would like to clarify something and it's that Kindle does not dictate from which store you can buy or choose from. Like I said, as long as the book is DRM free, you can buy and use mobi books directly or any DRM free ePub via Calibre conversion. I actually own and have books that I did not buy on Amazon. Granted, is easier to buy a book which comes on the native format, but Kindle users do not need to buy from Amazon only.
Although technically you're right, remember that the OP's primary language is Dutch. You cannot buy mobi books in Dutch anywhere, with or without DRM. Epub is the only format available (yes, and PDF, but who wants that on an ereader?).