The Book of Genesis is the first book in the Bible and the longest in terms of word count. It opens with the Christian creation story and the seven days God spent creating the world. The very first words of the book are “in the beginning.”
Given what the Book of Genesis covers and its placement at the very front of the Bible, most Christians assume that Genesis is the oldest book. That honor, however, belongs to the Book of Job. Job was written in approximately 1500 B.C. Genesis, on the other hand, was written during the Babylonian exile in the 6th century. Exodus was written around this same time as well.
Genesis is also very similar to a previously existing Canaanite work called the Enuma Elish. This mythological tale details the Canaanite creation story and shares language with Genesis. This has led many scholars to believe that the Enuma Elish influenced the writing of the Book of Genesis, even if the author merely borrowed the style and phrasing from the Canaanite tale.