This is an important passage. We have the birth of Ishmael. We have the covenant with Abraham and Sarah, and related name changes. We have circumcision, a visit from an angel--but only to Hagar--and we have God bargaining with Abraham about how many good people need to be found in Sodom.
What jumps out at me most is why Sarah is so badly treated in this passage. We have the motif (trope?) of the two women who are jealous of each other. So, Hagar runs away only to have an angel fetch her back. (Gen. 16:6 and as near as I can tell the only reference to an "angel" in this passage.) Then, despite the fact that Abraham literally laughs at God when he tells Abraham that Sarah will be a mother, and in that passage it is identified that Isaac will be named "he laughs," Gen. 17:17-18, we need this story about Sarah laughing, and then for kicks lying about it to God. Gen. 18:10-15. Recall, that Sarah is just overhearing promises from three travelers; Abraham laughed directly at God.
These passages are not fairy tales. They are told with an attempt to include real people, and as such, biases and caricatures of the culture find their way into the story. It is noteworthy that the editors could no choose whether to identify Abraham or Sarah's laughter as the source of Isaac's name: so they listed both.