I'm designing an alien society with a low population density. I intend for them to have 1 book per topic per place; books update annually as new information arises. I call them books, but they can even be large epigraphs and are stored in optimal conditions (e.g., in a cool, dry, and dark room where they are made and treated with care and cured of mould and insects regularly with little air but many preserving chemicals). If your method requires conditions that aren't described here, tell me.
All books are on/in:
- Hard drives and the Internet, which are rewritten frequently to prevent data corruption and loss
- 1 national library
- Archives (e.g., underground in bunkers)
- Possibly off-planet on extraterrestrial missions as necessary, and
- Citizens' houses.
However, despite updates, if I still want them to be preserved forever or for as long as possible, what substance do I use? Note that I suspend disbelief within reason as long as a substance may theoretically be inscribed upon and fit into a single planet and preferably a single city, so aluminium, graphene, sapphires, etc. are options. My reasoning is that my species is focused on scientific advancement and probably won't want to be tasked with repairing broken books after each decade.
Note on Physics: I don't care about Heat Death. I just want the best book materials within this universe. If that means replacing them every few centuries, so be it, but I want replacement to happen as little as possible.
Edit: Upon prompting, I have changed the word "epigraphies" to "epigraphs," which I mention to avoid confusion. Someone else has changed the wording and formatting a little bit before I could find the time to do it, which I would like to thank them for. If any of this impacts your answer, bear it in mind.