Genesis appears to be structured around the recurring phrase elleh  toledot, meaning “these are the generations,” with the first use of the  phrase referring to the “generations of heaven and earth” and the remainder  marking individuals—Noah, the “sons of Noah”, Shem, etc., down to Jacob.^[6] It is not clear, however, what this meant to the original authors, and most  modern commentators divide it into two parts based on subject matter, a  “primeval history” (chapters 1–11) and a “patriarchal history” (chapters  12–50).^[7] While the first is far shorter than the second, it sets out the basic themes and  provides an interpretive key for understanding the entire book.^[8] The “primeval history” has a symmetrical structure hinged around chapter 6–9,  the flood story, with the events before the flood mirrored by the events  after.^[9] The “patriarchal history” recounts the events of the major patriarchs Abraham,  Isaac and Jacob, to whom God reveals himself and to whom the promise of  descendants and land is made, while the story of Joseph serves to take the  Israelites into Egypt in preparation for the next book, Exodus.

Summary

God creates the world in  six days and consecrates the seventh after giving mankind his first commandment:  “be fruitful and multiply”. God pronounces the world “very good”, but it becomes  corrupted by the sin of man and God sends a deluge (a  great flood) to destroy it, saving only the righteous (Noah) and his family, from whose  seed the world is repopulated. Man sins again, but God has promised that he will  not destroy the world a second time with water.
God instructs Abram (the future Abraham) to travel from his home  in Mesopotamia (modern Iraq) to the land of Canaan. There God  makes a covenant with Abram promising that his descendants shall be as numerous  as the stars in the heavens, but that they shall suffer oppression in a foreign  land for four hundred years, after which they shall inherit the land “from the  river of Egypt to the  great river, the river Euphrates.” Abram’s name is  changed to Abraham and that of his wife Sarai to Sarah, and circumcision of all males  is instituted as the sign of the covenant.
Sarah is barren, and tells Abraham to take her Egyptian handmaiden, Hagar, as a concubine.  Through Hagar, Abraham becomes the father of Ishmael. Abraham asks God that  Ishmael “might live in Thy sight,” (that is, be favored), but God replies that  Sarah will bear a son, who will be named Isaac, through whom the covenant  will be established. At Sarah’s insistence Ishmael and his mother Hagar are  driven out into the wilderness, but God saves them and promises to make Ishmael  a great nation.
God resolves to destroy the city of Sodom for the sins of  its people. Abraham protests that it is not just “to slay the righteous with the  wicked,” and asks if the whole city can be spared if even ten righteous men are  found there. God replies: “For the sake of ten I will not destroy it.” Abraham’s  nephew Lot is saved from the  destruction of Sodom, and through incest with his daughters becomes the ancestor  of the Moabites and Ammonites.
God tests Abraham by demanding that he sacrifice Isaac. As  Abraham is about to lay the knife upon his son, God restrains him, promising him  numberless descendants. On the death of Sarah, Abraham purchases Machpelah (modern Hebron) for a family  tomb and sends his servant to Mesopotamia to find among his relations a wife for  Isaac, and Rebekah is chosen. Other children are born to Abraham by another  wife, Keturah, among whose descendants are the Midianites, and he dies in a  prosperous old age and is buried in his tomb at Hebron.
Isaac’s wife Rebekah is barren, but Isaac  prays to God and she gives birth to the twins Esau, father of the Edomites, and Jacob. Through deception, Jacob  becomes the heir instead of Esau and gains his father’s blessing. He flees to  his uncle where he prospers and earns his two wives. Jacob’s name is changed to  Israel, and by his wives Rachel and Leah and their handmaidens he has  twelve sons, the ancestors of the twelve tribes of the Children of Israel, and a  daughter, Dinah.
Joseph, Jacob’s favourite son, is sold into slavery in Egypt by his jealous  brothers. But Joseph prospers, and when famine comes he brings his father and  his brothers and their households, seventy persons in all, to Egypt, where  Pharaoh assigns to them the land of Goshen. Jacob  calls his sons to his bedside and reveals their future to them before he dies  and is interred in the family tomb at Machpelah. Joseph lives to see his  great-grandchildren, and on his death-bed he exhorts his brethren, if God should  remember them and lead them out of the country, to take his bones with them. The  book ends with Joseph’s remains being “put in a coffin in Egypt.”