There are several differing opinions on the origins of the Book of Genesis. The religious folk believe the work was written by Moses during a conversation he had with their Lord God. My version of The Bible features the Book of Genesis as being titled thusly, The First Book Of Moses Called Genesis.
Not all Biblical scholars agree that Moses wrote the Book of Genesis, nor the four other books that make up the Torah, or Pentateuch. Throughout the 20th Century most scholars agreed that these five books, Genesis, Exodus, Leviticus, Numbers and Deuteronomy, originate from four sources. The Yahwist: this source receives its name from the fact that God is sometimes referred to as Yahweh, or to be more accurate YHVH, in most English translations of The Bible YHVH is replaced with ‘the Lord’ or more simply ‘God.’
The Yahwists parts of The Bible were believed to date from about 950 B.C.E. but now it’s thought they might be as late as the 6th or 5th centuries B.C.E., which was the period of Jewish history known as the Babylonian captivity, or exile. During this time period the Jews of the Kingdom of Judah were held as captive in Babylon, obviously.
Another source is known as the Elohist, which derives its name from the term Elohim, which is used to identify God. In many parts of the Hebrew Bible in which this term is used it’s use is to describe not a singular God, but a pantheon of gods, or powers. This Elohist interpretation of God could be considered quite an abstract version. Originally the term Elohim, or El, was that used for God before the story of Moses, after which God is referred to as YHVH. This Elohist version of God is seen to be a being capable of sympathy and regret, unlike the YHVH version, and to begin with God, as Elohim, appears in person throughout Genesis.
In the Elohist tale of Abraham, he, Abraham does sacrifice his son Isaac. Later stories revised this version, and allowed Abraham to substitute a ram in place of his son. There are other differences between the different sources.
The third source is called, the Deuteronomist, this source is regarded as being from a school of authors, rather than from a singular source. During the middle of the 20th Century scholars identified that the Deuteronomist school were Levites from the country. Levites are members of the tribe of Levi, both Moses and his brother Aaron, obviously, were Levites.
This source primarily concerns itself with the covenant between Israel and Yahweh. The peoples of Israel, originally the character Jacob, Yahweh decided that Israel and his people are the chosen people of God, and Yahweh demands that Israel and his people live according to his Law.
The fourth source is called the Priestly source, and is a product created after the Babylonian captivity, when Judah was a province of the Persian Empire, around the 5th Century B.C.E. it was intended to show the Jews that though everything seemed bleak, all hope lost, God had not abandoned his chosen peoples. His covenant with the folk of Israel had remained strong.
These four different sources contain many contradictions, inconsistencies and repeat the same ideas, one of the many contradictions is the various names of God, a singular God, who is referred to differently throughout the four sources, as though each source refers to a very different God. There are, for example in this Book of Genesis, two different creation myths.
Overall, the Book of Genesis is regarded as an antiquarian work of history, perhaps the best of its type, a form of literature that concerns itself with the origins of the world, the first humans and stories of ancestors and of heroes.
For more information on the origins of the Book of Genesis these websites are recommended: