Sumerian is an oddball of ancient languages. It might never have been deciphered if not for a happy circumstance I’ll mention below. Other languages important to the history of mythology and religion largely fall into two categories: Into-European (Sanskrit, Old Persian, Greek, Latin) and Semitic (Akkadian, Amorite, Eblaite, Phoenician, Ugaritic, Arabic, Hebrew). But Samuel Noah Kramer says of Sumerian that it “stands alone and unrelated to any known language living or dead” (Sumerian Mythology, 1961, Harper and Row). How did we decipher it, then, and why was it worth the trouble? As to how, we are very fortunate that the Akkadian speaking peoples who followed the Sumerians revered the language and wrote interlinear texts with Akkadian translations of Sumerian compositions. As to why, the answer is simple and profound: the great myths and religious concepts of Mesopotamia, so foundational to numerous later cultures, were born in ancient Sumer.
I'm a fantasy fan and I'll bet you are too. I also am in the early stages of building a fantasy world and writing stories and novels. It will be a world like Mesopotamia and my goal is to create something immersive like the best fantasy worlds out there.