If we can legally publish a book, and it isn't in the archives, it's because no volunteer has produced it yet. At the moment, we have a predominance of English language novels because that is what most people have chosen to work on.
We're always looking for new languages and topics, and always delighted to see people producing them. If we don't have enough of the types of books you would like to see, why don't you help us out by contributing one? If the people interested in a particular area don't contribute, we'll always be short in that area.