This is something that worried people for a long time. For how long will the information last- and if it will decay, how? We have some wonderful examples of a long preservation. We will not talk about cave wall art (which is perhaps 45,000 years old) and information written in stone, such as Rosetta Stone (196 BC). The oldest way to write something that would resemble books was on three Ps: Papyrus, Parchment and Paper. Papyrus is the oldest media known to men. The oldest papyrus that was dated is about 4500 old and the text is still readable. The Yuya Papyrus shown in this website, made in beautiful color is dated at 1390 BC. Fast forward and Dead Sea Scrolls found in 1950s, are as old as 300 BC, were written partially on parchment and partially on papyrus; the content of biblical texts is still readable and authentic, according to the scholars.
Paper as we know it was invented in China and the oldest paper document (a map) is dated 179 CE.
Whenever documents degrade, it is rarely due to the fade of inks. Most commonly, the media itself degrades due to rot or to fire.