I never read The Da Vinci Code. To give you some insight into how uninterested I am in the book/movie, I actually had to google how to spell "da vinci." I thought it was "davinci." Spell checker disagreed. Anyhow, I never read the book, but my wife did, and every once and a while she'd lean over and say something along the lines of, "Read this; is this true?" One of those times had to do with the author arguing that ancient Israel had never been monotheistic. As is often times the case with historical fiction, it's true and not true. It doesn't take long when reading through Deuteronomic history to realize that the nation of Israel repeatedly struggled to decide if it would be monotheistic or polytheistic. Most of the time, at least leading up to the Babylonian Exile, polytheism won out.
Think about it. The book of Judges is just one long story of Israel worshiping Canaanite gods and paying the consequences. In I Samuel, the first king of Israel, Saul, seems to be monotheistic, but would rather serve himself than God in the end. It's not until we reach David that the nation of Israel has a truly monotheistic king that leads the Israelites into an age of monotheism. How long does that age last? Well, until David's son comes into power.
Solomon begins his reign supporting his father's monotheism, but soon becomes polytheistic to support his wives' religions. Solomon was beyond politically savvy, but the alliances he made to bring the nation of Israel power and wealth also brought Israel Molech, Chemosh, Baal, Astarte, and Milcom, to name just a few of the foreign gods and goddesses he married into. As punishment, God strips the ten northern tribes away from Solomon's son and gives them to a servant in his son's government. However, Jeroboam (the new northern king) immediately sets up golden bull idols at the northern and southern borders of his territory so that his new subjects won't have to travel back the Jerusalem temple to worship God. In what I find an example of true irony, Jeroboam calls these golden bulls idols of Israel's God, but bulls were the embodiment of Apis and Baal, Egyptian and Canaanite gods. So, surprise of surprises, the northern tribes leave monotheism behind and never go back.
The southern kingdom wasn't any better. It wasn't until four kings after David that another monotheist comes to power in Judah. The only other two that are coming to mind right now are Hezekiah and Josiah. I'm probably forgetting one or two, but most of the southern kings were polytheistic also. But in spite of all of this, I still say one cannot blithely make the argument that ancient Israel was a polytheistic nation attempting to become monotheistic (as many who are bias against traditional Judeo-Christian would argue). It is still possible to argue that ancient Israel was formed on the foundation of monotheism but had a hard time maintaining that position considering they would have been absolutely alone in their theology.
Either way, one of the major tensions driving I & II Kings is the internal conflict between monotheism and polytheism. As we'll find out by the end of II Kings, polytheism wins, but the cost of that victory was the loss of the nations of Israel and Judah.
Stopping point: I Kings 20