Eternity in Their Hearts by Don Richardson is a great insight into the scattered tribes of Israel and how so many cultures, some of which are polytheistic, were rooted monotheism.
http://www.donrichardsonbooksales.com/
related subject
http://www.stevenmcollins.com/html/decalogue_stone.html
Don preaching on the subject:
https://www.youtube.com/watch?v=Z6pzUwBaGvw