Answer:
Because the Epic of Gilgamesh is a great literary work, and is one of the oldest religious and epic poems.
The Epic was written in Sumer in around 2,100 BC, and narrates the story of Gilgamesh, the king of Uruk (the Sumerian capital at the time) who has to face a variety of circumstances and enemies.
The story has drawn the attention of historians, linguists, archeologists, and writers. It has also attracted the attention of theologicians, because of its similarities with several parts of the Hebrew Bible.
