There wasn't much bookbinding to do with the first books, because of course, they were clay tablets. When people got serious about the need to preserve information, written language appeared on the scene. This happened around 3500 BC when the ancient Sumerians began using cuneiform to record information in clay. Cuneiform consists of wedge-shaped marks, made by pressing a square stylus onto a wet clay surface. After the writer was finished, the clay would be left to dry in the sun or baked in an oven. They also made clay tubes or "slipcases" for the tablets; when the tablet was being stored, it could be inserted into a slipcase for protection. Tablets of this sort were made by the Babylonians, Sumerians, as well as the Assyrians. There were thousands of these clay books at the royal library of Nineveh (Assyria), covering an incredible range of topics like astronomy, mythology, geography, etc. (Source: Creative Bookbinding by Pauline Johnson, p.4-5)
So although we've moved beyond clay tablets for preserving important documents, we can still play with the process. LadyArtisan does some fabulous book covers using polymer clay. I think the ancient Sumerians would love this!