Who wrote the original version of the Bible?

God is the author of the words in Scripture. It began orally in the Garden of Eden between God and Man. It may have been written on tablets as one theory surmises. It was codified by Moses during the Exodus period and continued onwards until the final chapter, the Book of Revelations was completed by the writer John. Sometime after this, men came together to decide the 'New Testament' just like they did for the Old Testament before it. In all, there were many different recorders/writers of Scripture but all had God as the inspired Word and author.
The bible was written over many centuries by many different people who wrote recollections of religious events or experiences involving God.