Coming from a rich vein of deluge stories that includes the saga of Utnapishtim, as related in the Epic of Gilgamesh, and the story of Deucalion and Pyrrha in Greek myth, Noah's story is one in which the world has become so wicked that God decides to flood it, and wipe out not only humanity, but also all the animals, sparing only Noah and his family, and the animals that Noah takes on the Ark with him. Modern creationists have added a lot more detail about the first hibernation, a collapsing vapor canopy that had been letting people live hundreds of years, dinosaurs and fossil fuels, and all sorts of other fun stuff not found in the original story but still useful for making the book sound more scientifically plausible.
Well, OK; if that's your thing, I won't argue with you. But I personally find that the story of Noah presents what is probably the best illustration of the Documentary Hypothesis. Developed in the 18th and 19th centuries by Bible scholars puzzling over some of the disparities in the Torah, the documentary hypothesis says that much of Genesis is spliced together from two earlier stories, one that used the divine name YHWH and the other that used the more common name Elohim. (In Hebrew, YHWH is the name used exclusively for God; elohim is a more generic term, like the English word god.)
The Yahwist version of Noah's story would go something like this:
When men began to multiply on the face of the ground, and daughters were born to them, 2 the sons of God saw that the daughters of men were fair; and they took to wife such of them as they chose. 3 Then the Lord said, “My spirit shall not abide in man for ever, for he is flesh, but his days shall be a hundred and twenty years.” 4 The Nephilim were on the earth in those days, and also afterward, when the sons of God came in to the daughters of men, and they bore children to them. These were the mighty men that were of old, the men of renown.
5 The Lord saw that the wickedness of man was great in the earth, and that every imagination of the thoughts of his heart was only evil continually. 6 And the Lord was sorry that he had made man on the earth, and it grieved him to his heart. 7 So the Lord said, “I will blot out man whom I have created from the face of the ground, man and beast and creeping things and birds of the air, for I am sorry that I have made them.” 8 But Noah found favor in the eyes of the Lord.
Then the Lord said to Noah, “Go into the ark, you and all your household, for I have seen that you are righteous before me in this generation. 2 Take with you seven pairs of all clean animals, the male and his mate; and a pair of the animals that are not clean, the male and his mate; 3 and seven pairs of the birds of the air also, male and female, to keep their kind alive upon the face of all the earth. 4 For in seven days I will send rain upon the earth forty days and forty nights; and every living thing that I have made I will blot out from the face of the ground.” 5 And Noah did all that the Lord had commanded him.
n the six hundredth year of Noah’s life, in the second month, on the seventeenth day of the month, on that day all the fountains of the great deep burst forth, and the windows of the heavens were opened. 12 And rain fell upon the earth forty days and forty nights. 13 On the very same day Noah and his sons, Shem and Ham and Japheth, and Noah’s wife and the three wives of his sons with them entered the ark, 14 they and every beast according to its kind, and all the cattle according to their kinds, and every creeping thing that creeps on the earth according to its kind, every bird according to its kind, every bird of every sort; 15 and the Lord shut him in.
17 The flood continued forty days upon the earth; and the waters increased, and bore up the ark, and it rose high above the earth. 18 The waters prevailed and increased greatly upon the earth; and the ark floated on the face of the waters. 19 And the waters prevailed so mightily upon the earth that all the high mountains under the whole heaven were covered; 20 the waters prevailed above the mountains, covering them fifteen cubits deep. 21 And all flesh died that moved upon the earth, birds, cattle, beasts, all swarming creatures that swarm upon the earth, and every man; 22 everything on the dry land in whose nostrils was the breath of life died. 23 He blotted out every living thing that was upon the face of the ground, man and animals and creeping things and birds of the air; they were blotted out from the earth. Only Noah was left, and those that were with him in the ark. 24 And the waters prevailed upon the earth a hundred and fifty days.
6 At the end of forty days Noah opened the window of the ark which he had made, 7 and sent forth a raven; and it went to and fro until the waters were dried up from the earth. 8 Then he sent forth a dove from him, to see if the waters had subsided from the face of the ground; 9 but the dove found no place to set her foot, and she returned to him to the ark, for the waters were still on the face of the whole earth. So he put forth his hand and took her and brought her into the ark with him. 10 He waited another seven days, and again he sent forth the dove out of the ark; 11 and the dove came back to him in the evening, and lo, in her mouth a freshly plucked olive leaf; so Noah knew that the waters had subsided from the earth. 12 Then he waited another seven days, and sent forth the dove; and she did not return to him any more.
20 Then Noah built an altar to the Lord, and took of every clean animal and of every clean bird, and offered burnt offerings on the altar. 21 And when the Lord smelled the pleasing odor, the Lord said in his heart, “I will never again curse the ground because of man, for the imagination of man’s heart is evil from his youth; neither will I ever again destroy every living creature as I have done. 22 While the earth remains, seedtime and harvest, cold and heat, summer and winter, day and night, shall not cease.”
18 The sons of Noah who went forth from the ark were Shem, Ham, and Japheth. Ham was the father of Canaan. 19 These three were the sons of Noah; and from these the whole earth was peopled.
It is interesting how well and how easily this reads; if you look at the original story and cut out the parts that reference YHWH, you'll find an eminently readable Elohist version of the story.
The documentary hypothesis was developed in the 18th and 19th centuries, and these days is pretty much taught as a given in seminaries and other university settings, though I won't claim that it's universally accepted. There are a number of Bible colleges that still contend that Moses wrote the first five books of the Bible.
What else to say about this passage that hasn't been said a billion times? Structurally it repeats the theme of sin and divine judgment, although in this case, people aren't exiled from God's presence as Adam and Eve were, nor from the company of other humans, as Cain was. This time it is a final and absolute judgment, where the entire planet is drowned. (The writer of the Petrine epistles also tells us that Noah steadfastly warned the people of his age about the impending judgment up until the day the flood came.)
What is interesting is that in this case, we see the divine judgment also acting as a means of renewal or redemption. The language used in the blessing of Genesis 9:1-5 mirrors the blessing found at the end of Genesis 1, another Elohist passage. In both cases, God blesses the people, tells them to be fruitful and multiply. and tells them what they can eat. In Genesis 1, God allowed people to eat any plant; here, he allows them also to eat animals. Se we see (in a sense) a sort of eucatastrophe, in which the undeniably horrible catastrophe of worldwide flood brings about something good, namely a return not to Eden but to something similar or approximate. It's as though the wickedness of humanity has been washed away from the earth -- essentially what the author of the Petrine epistles talks about when he refers to the earth as having been baptized in the days of Noah.
I do find it interesting that the Yahwist material is what refers to the sacrificial animals, which (admittedly) makes sense since it was the Levite priesthood that became most closely associated with Temple worship, and it was Moses the Levite to whom the Name was revealed in Exodus 3:13-15. The Elohist material simply refers to two of every kind of animal coming to Noah to be loaded onto the ark, while the Yahwist material has Noah being told to go out and fetch the animals, including the clean sort that will be required for sacrifice.
Beyond that, this passage of the Bible is sandwiched with two odd anecdotes. The first is the sons of God and the daughters of men, and the Nephilim, their offspring. The second is that odd incident with Noah getting drunk and his son Ham seeing him lying naked on the floor of his tent, and getting cursed for it, just like Cain did. They're both odd, though as far as that goes, the Nephilim story takes the cake.
The passage talks about the sons of God, which often gets used to refer to angelic beings, as in Job 1. It also gets used as a euphemism for the righteous, those who walk with God and seek justice. Jesus himself even uses the term to describe those who work for peace, in the Beatitudes.
I regret that I've heard a few people say that the opening verses of Genesis 6 describe a situation where the descendants of Seth are marrying the descendants of Cain. What's troubling about this? For starters, it completely misses the entire notion of personal accountability for one's own actions, and claims that righteousness (being a "son of God") is dependent upon one's ancestry. That's just messed up, and goes against the teaching found elsewhere in the Bible, like the book of Ruth or the teachings of Jesus himself.
The other explanation is that we're supposed to assume that angels were having children with human women, like a bunch of Greek gods running around raping young women so that they could have heroic children like Perseus or Heracles. Whether it was this or the commingling of racial lines, it's pretty clear that God didn't like it, since it's right after this is reported that we read God decided to wipe everyone out. (Or maybe it was that the people revered the Nephilim as heroes.)