Genesis 15 and 16 are today's readings. There's two major events, one for each chapter.
First, Genesis 15 provides us with the formal initiation of a covenant between Abram and God. Abram expresses his concern that his household will die out with him. After all, Lot has gone his own way and Abram has no children of his own. The custom of the time suggests that his chief servant would inherit, though I saw one source that suggests this would have been a stewardship until another person of greater social standing came along.
That is, if everything had passed to Eliezer, the household would have ceased fairly soon. Either the servants and slaves would have been free to depart or another "great" person would have taken over for him. Either way, it looks to Abram like God's promise is pretty well done for.
God, though, has a different purpose. Before we go any farther, though, take note of those small caps where the word "Lord" is (or "God" in the combination "Lord God"). You're dealing here with the divine name of God, not some generic deity of no certainty. Remember that: God makes His covenant in His own name.
The covenant ceremony, a symbolic action demonstrating the lifelong commitment, takes place in a dream for Abram. As you reach the end of Genesis 15, you see the promise of God that Abram's descendants will possess everything from the edge of Egypt to the Euphrates River. It takes some time--nearly 100 years--but this does come to pass.
The next chapter is a bit more tragic. Sarai suggests to Abram that he father a child through her slave, Hagar. This may have been a custom at the time, in may have been an idea picked up in their wanderings. (It does seem to have inspired the dystopian writings of The Handmaid's Tale, a work typically seen as showing a future if Christians run the world, though it's based in this story which foreshadows Islam.)
Either way, Hagar is treated badly here. She is the focus of this story--she conceives, is thrown out from the family, but then God reveals Himself to her. She is one of the few women in the Patriarchal Age (really until the time of the Judges) that speaks with God.
The unfortunate downside is that Abram, by fathering a son who would not be the one of the covenant, ends up bringing into being a line that eventually becomes antagonistic to his other descendants. Family ties run deep in many places, and Israel, Arabia, Jordan, and the rest of the modern Middle East is one of those places. Many of the Arab peoples trace their lineage to Ishmael (and some to Esau), while the Israelis trace theirs to Isaac, who comes later. It's a family feud that has run for millennia.
(for more on Sarai/Sarah and Hagar, check out Vindicating the Vixens, chapters 7 and 8)