I think the bible has originated from simple family tales to that of symbolic religous text followed to the word by billions. At a time in history when families and communities had only the entertainment of togtherness and discussion, came the birth of tales and stories to help familes and communities become whole, to live happy lives of strong morals and beliefs. These stories would be past down thorugh many generations, but the original story in it's first state could have been fiction, non fiction or a mixture of the two, I can only hope it was that of true events that have been retold, and relived time after time, to strengthen society, and secure a future for the moral lifestyle that has survived all these years.
Therefore in answer to your question: who wrote the bible - well billions, the 'tales' the 'fights' the 'morals' and the 'beliefs' of the bible are that of billions of people recalling them time after time, those stories may have then been put down on paper but the writer was just another person to translate, describe, and depict the scenes that we would never no had existed without the word of mouth and later 'THE BIBLE'