According to several scholars, the first chapter of Genesis (and several others) was written by a Jewish elite who objected to the surrounding religions (some scholars think Ch1 was written during the Babylonian exile), and was thus written in a way to refute these religious beliefs.
Genesis 1 has many similarities to several religious texts of the Ancient Near East, particularly the Babylonian Enuma Elish. For example, the order of creation is almost exactly the same, things are brought into existence by spoken word, and so on. However there are substantial differences.
A very quick overview of the Enuma Elish: there were two original water gods Apsu and Tiamat who have lots of children. Eventually, some of the gods kill Apsu and Tiamat wishes to take revenge. Their grandson Marduk, the god of wind has a battle with Tiamat and kills her, creating the world out of her body. Humans were created to run this new creation.
So, in Genesis 1, we have an opening where God is there at the beginning. This is different from Near East creation stories since it lacks a theogony, or any history of the gods. God is just there, not born, not created, he's just there. In verse 2, there are two things to point out: "The earth was formless and empty", we're given two ideas here, formless and empty, which is important when considering the order of creation. The second part of verse 2 seems to establish an apparent background to an upcoming battle between the deep (a reference and in Hebrew, a cognate, with "Tiamat") and the "ruah Elohim", literally the "wind of God" (see Marduk) but often translated as "spirit of God". However, this epic battle as found in the Enuma Elish, which is described in some detail there, never materialises. Instead, God is in absolute control, and just procedes with a nice orderly creation.
So, the creation itself: there are 6 days of creation. If you draw a two-column table, and on the top of the first column write "formless" and on the top of the second column write "empty" and then put the first three days in the first column and days four to six in the second, then you'll see a pattern emerge. Day 1: God creates light (form) corresponds to Day 4: God creates the sun, moon and stars (content). This idea that the order of creation isn't literal, but following a conceptual model of form-content is called the framework hypothesis. With this, it highlights that God has a plan and that creation is following an orderly purpose. This is particularly emphasised by the fact that "God saw it was good" appears six times and "very good" once (a total of seven times, the Hebrew magic number).
We also see in the creation account that celestial bodies, as well as monsters of the sky and sea were created by Gods, emphasising the monotheistic Hebrew mindset as in neighbouring religious beliefs the celestial bodies as well as sea monsters (i.e. Tiamat) were often divine.
We also see that humans were created in God's image, serve a purpose and are given an inherent dignity through this. In neighbouring religions (such as, again, the Enuma Elish), humans are nothing more than slaves to start but eventually things get better. In Genesis, things start good and get worse. Note here that men and women are created at the same time.
As you can see, Genesis 1 can be seen as a polemic against neighbouring religious beliefs highlighting several important aspects of Jewish and Hebrew theology:
- the omnipotence and sovereignty of God
- God as an eternal monotheistic God
- the order and goodness of creation as opposed to a haphazard creation stemming from violence
- humans as a being created by God in his image, with a sacred value and as the pinnacle of creation.
Genesis 1 however ignores the more intimate nature of God, such as his personal relationship with man, areas of God's character that are addressed in chapter 2.
Creation according to Genesis is therefore in my opinion not a literal step by step manual to creation but an account of creation constructed to highlight several truths about the nature of God. It should therefore not be considered a scientific treatise but actually an intelligently constructed literary text. In fact, I think people from both side of the fence (Christians and atheists) view the creation account in a rather patronising way by refusing to dig deeper into the creation account by asking questions such as, "why is it structured like this?" "why does it mention this?" and therefore fail to see how intelligent it actually is.
Edit: Several church fathers, such as Origen, believed in a non-literal interpretation of Genesis 1. In fact, the more literal interpretation is probably quite recent and possibly as a backlash against scientific theories and attacks against Christianity.