Letters enclosed in clay envelopes, as well as works of literature, such as the Epic of Gilgamesh have been found. Historical accounts have also come to light, as have huge libraries such as that belonging to the Assyrian king, Ashurbanipal (668-627 B.C.E.).
Cuneiform tablets at The British Museum
They furnish us with materials for the complete decipherment of the cuneiform character, for restoring the language and history of Assyria, and for inquiring into the customs, sciences, and … literature, of its people.