Job 33:14  "For God speaketh once, yea twice, yet man perceiveth it not.

and again... Job 11:6 "And that he would show thee the secrets of wisdom that they are double to that which is. "

I am convinced that the "doubling" of Bible Books is a part of and an indicator of prophetic design. For example, first and second ---- Samuel, Kings, Chronicles, and the duplicate new testament books. They hold secrets to the future. 

There are also exactly eight names spread throughout scripture which are "doubled.". Abraham, Abraham. Jacob, Jacob. Moses, Moses. Samuel, Samuel. Martha, Martha. Simon , Simon. My God, My God. and Saul, Saul. There is a prophetic connection which is yet to be found in these names.