Although the preservation of books is not easy, in ancient times, people had the habit of using objects when they were buried, so a considerable number of books were buried underground with their original owners. If the environment is dry, ancient books such as bamboo slips, wooden slips and silk books can still be preserved. This kind of book can't be exposed to the air for a long time after it is unearthed. Once exposed to the air, the environment will change greatly, and such books will easily rot and deteriorate immediately, and the words on them will fall off very seriously. You can watch the video of Yunmeng Qin bamboo slips unearthed, but it's a pity to watch it.