The bible is a collection of texts that encompass a whole range of literature, poetry, history, law, and analogy and song. It is not the literal word of God, neither is it simply a bunch of stories......
The crazy thing about American Biblical Literalism is much of what they hold to be true and foretold by the Bible, the Rapture being a prime example, are not even in the Bible....the Rapture being largely a 15th century invention of a man who liked to hang young women for witchcraft. Only the other day I was talking to someone supposedly who went to a seminary that actually believed that God gave the Septuagint to Jesus, who passed it onto Paul of Tarsus....
My point is that don't take these people's opinion as gospel (

) when judging the Bible or what it is supposed to be, which ultimately is as a guide to an individuals spirituality and relationship with their God. Because of the nature of the Bible it is practically impossible to say this or that is definitively the purpose of the bible, as that is subjective to the individual to a great extent and in a good many cases what American (and others) Evangelicals believe has little to do with the Bible and everything to do with their politics and prejudices.