Absolutely, I didn't mean to suggest that every single Mesopotamian thought that the Epic of Gilgamesh was the truth. But even looking at non-devout Christians

Absolutely, I didn't mean to suggest that every single Mesopotamian thought that the Epic of Gilgamesh was the truth. But even looking at non-devout Christians today, I don't think many of them would call the Bible a work of fiction - they view it as something less than an accurate account of history, but not at all as fictional. I would bet that if you asked the majority of Christians, even the non-practicing ones, they'd believe Noah was a real person who really did worship God, and maybe even faced some kind of flood, and probably lived to an old age - even when they don't believe that he built an arch that literally housed two of every animal on Earth to traverse a global flood, or that he lived for 900+ years.