Enuma Elish (named for its first two words, meaning "when on high") is the Babylonian creation epic. It is related to the Genesis creation account (some would say "lies behind it") and is gripping reading. It's old (probably dates to around 2000 B.C.E.) and introduces world-shaking protagonists like Marduk, grotesque human progenitors like Kingu (whose blood, drop by drop, turned into mankind), weird magical-cult items (the Tablets of Destiny, worn on the chest and possible predecessor of the Hebrew Urim & Thummim), the Assembly of the Gods and that perennial favorite of dungeon-crawlers the world over, Tiamat.
You can find it in various editions and collections, including this convenient classic anthology.