This story is much more important than the stories that come before it. You can see that in the fact that it is about as long as all the earlier stories in Genesis put together. There's an important shift here. Up until now we've seen God dealing with the whole world. We've also seen, in story after story, from Adam and Eve, ot Cain and Abel, to the World before the Flood, to the Tower of Babel, the world has been rebellious and unresponsive to God's call. It's been a difficult relationship and the old methods haven't worked so now we see God try something different.
The story of Abram is the story of God forming a special relationship with one person, one family, and one people. This isn't with the idea that Abram and Sarai are somehow better or more deserving than other people. The idea seems to be that God has to start somewhere. But that doen't mean that the blessing is only for Abram and his descendants. From the very first the story makes it clear that this blessing, all the people of the world shall be blessed.
Abram is an odd choice for a hero. He isn't particularly strong, brave, wise, or anything of the sort. The one thing that sets Abram apart is his faith. when he is called out of his ancestral home by God, he goes. Abram's trust in God will falter fairly often in during his story and he often misunderstands what God is calling him to do. Still, this deeply flawed man always holds on to this relationship to God and that becomes his one saving grace.
If God is shown to be reliable in this story, Someutes his wife in this chapter is proof of that. Perhaps the only praiseworthy thing about him is his faith.
We are told that Abram is 75 years old in this story. By implication, Sarai would be 65. The age here isn't literal; it goes to underscore the idea that the couple are barren. They comes from a culture where there is no idea of an afterlife. The only kind of immortality they are aware of is the kind where your family and good name continue after you die. A childless couple in this culture is as good as dead and dishonered. Only a son could save them, and the scribes putting this story down want to make sure we know, a son is impossible.
It's no wonder Abraham is willing to grasp at any little bit of hope. When God offers him a son, numberless ancestors, and an honorable name that will last forever, that is literally everything that matters to a man who has nothing.
Abram and his family head out into the unknown based in faith in a promise from a God who he hasn't known accepts for what may be selfish reasons but, by accepting he becomes the first to participate in this new relationship.
While Abram is faithful, he's still not a very good man. When the family heads to Egypt, Abram effectively prostitutes his wife to the King of Egypt. Aram's excuse is that Sarai is so beautiful that Pharaoh would kill him and take her if he didn't do this. There is a hidden agenda, though, as we can see in verse 16.
Because of her, Abram got along very well: he accumulated sheep and cattle, male and female donkeys, men and women servants, and camels.
This sounds like a con game that Abram is running on Pharaoh, and one that he will repeat several times. It also sounds like God is complicit in this operation, and punishes Pharaoh for something that was clearly Abram's fault. That's hard for modern Christian readers to take and rightly so. It reflects a primitive, tribal understanding of God that is not consistent with what Jesus reveals to us about God.
In ancient times, the idea was that God only cared about the chosen people. This is an idea that the Gospels clearly reject in Matthew 3:7-10 any other places. God cares about all people and insists that his followers practice the kind of justice that honors this fact. That's something that the writer of this part of Abram's story didn't seem to understand.
Still, the bottom line of the Abraham story is still true. God is faithful to people, even when the people don't really deserve it.