'Exodus'

The Exodus is an amazing event. In that time, God made a people for himself, pretty much from scratch. God predicted the whole thing in Genesis. He said, "Know for certain that your descendants will be strangers in a country not their own, and they will be enslaved and mistreated four hundred years. But I will punish the nation they serve as slaves, and afterward they will come out with great possessions. You, however, will go to your fathers in peace and be buried at a good old age. In the fourth generation your descendants will come back here..." So, just as he said, God allowed his people to be slaves and then brought them out in great power.
I am not really sure why God allowed the Children of Israel, that is Jacob, the third patriarch I mentioned before, the grandson of Abraham, I'm not sure why his children became slaves in Egypt. Egypt has had a long history and has been and was at the time Exodus took place a powerful empire. I cannot say it was the Israelites fault, but I can and should mention an important reason why they were not in the land God promised them. In the fifteenth chapter of Genesis, God makes it clear that Abraham cannot take possession of this land that God has given him yet. He says, "In the fourth generation your descendants will come back here, for the sin of the Amorites has not yet reached its full measure." So it seems that God is mercifully putting off His righteous judgment a little longer, but He knows that the Amorites, which is also intended to insinuate their neighbors, will only get more wicked and the day will come when the Israelites will be able to act as God's instrument of justice to destroy a wicked people.
But I get ahead of myself. So the Exodus both prefigures the future redemption of mankind from sin all together and is the next step towards God making a refuge and an instrument for His holy agenda on earth.
The Israelites were slaves in an oppressive, idolatrous regime in Egypt and they showed God's righteousness and power in Egypt and God showed His power to Israel that they may believe. So God is simultaneously making a statement to a world that has rejected and forgotten Him that He is not dead nor is he done with mankind.
The second half of the book details the adventures that the people have under Moses and the beginning of the Law that he is setting out for them.