The problem is though; that the book was written by men. Written by many men, and most likely the original bible was very different - as over the years people have added their bits to it. Christians still follow this book as a Holy scripture; but what makes it holy? It's a book written by men who liked to think of themselves as the disciples of the son of God, God himself hasn't written any of this, nor is there ANY proof of the miracles that happened in the bible.
Christianity is based on the bible after all what else is there left relating to Christ? So... You take a huge dose of Paganism, you mix it with a "holy scripture" made in the middle east, add some changes that suited the needs of the people at the time - and you've got yourself a Religion. This religion is meant to be followed by nearly 1/3 of the world population.
This is why the bible shouldn't be used as a Moral guide - it has been tainted by far too many people. It's like a game of chinese whispers, and the kings present at the time pass the whispers onto each other, changing it as it suits them along the way. Don't forget that during much of the periods "after Christ," people were led by Monarchy, if they Monarchy didn't like something - they put it to bed.
There is also the small problem of the Bible actually being an incredibly aggressive text, whilst it promotes peace to thy neighbours and thou shalt not murder, God still actively encourages the death and suffering of Men.