The books would be effectively destroyed by leaky roofs / mold/mildew, bugs and rodents.

@RonJohn: Some. Nowhere near all.

The books would be rendered useless by future children not being taught to read beyond the basics (or at all). And a lot of those books assume much existing knowledge.

@R..GitHubSTOPHELPINGICE it doesn't have to be "all", it just has to be the ones near where "your" particular band of survivors live. And since Apocalypse survivors will probably be more rural than urban or suburban, there won't be many books anyway (just by the nature of not being many people).

@RonJohn: If you still have anyone older than young children from before the apocalypse alive, that will all be taken care of. They will know the language the books are written in and be able to figure out context, look for what they need to understand things they want to learn about. You really need the absence of anyone with language skills to read the books, or even the idea that books can contain ideas to learn about the real world from, in order to have any "hope" that the books will all rot before people recover large amounts of knowledge from them.

The 1% or so who knows how to smelt and forge or build a basic generator or incandescent light-bulb etc would be quite valuable. They will tend to be kept alive and protected for having this knowledge.

It wouldn't be that hard to push us back to before the industrial revolution actually. Fossil fuels are much harder to mine than they were back in the day, if our machinery gets taken out it's unlikely we could easily get steam engines easily back up and running. I'd say pushing us back to the Dark ages wouldn't be too difficult.

@Turksarama: Coal is a fossil fuel, and we have lots and lots and lots of it. It is only petroleum which is harder to get at now than it was 100 years ago. And anyway, hydropower works just fine, especially if the population is greatly reduced.

We have a lot of coal, but modern coal mines are much deeper than older ones and can't be easily mined with pickaxes and minecarts.

@Turksarama: Depends on what specific mines you have in mind. There are lots of places where lignite is extracted by surface mining. (And not even in faraway exotic places beyond the seas, but here in Europe.)

@Turksarama I'm pretty sure steam engines can run on charcoal.

@AlexP, "surface" is relative. Judging from pictures of the mines, a typical surface mine will have around a hundred meters of overburden to remove before you get to the coal -- something that would be considered an extreme deep-level mine by pre-industrial standards.

@Hearth, steam engines can run on anything that'll burn. The problem with charcoal is that it is a very land- and labor-intensive fuel source.

@Mark Sure, but the premise that you couldn't run a steam engine without fossil fuels isn't true.

Just like how papyrus scrolls have survived up to today, books will survive in desert areas. But knowing how to read them requires practice which won't happen in most places. In order to keep knowledge, there has to be enough people around so that rarely needed knowledge is kept by scholars.

@R..GitHubSTOPHELPINGICE "If you still have anyone older than young children from before the apocalypse alive, that will all be taken care of." The Western European Dark Ages (where almost everyone -- even those with parents who knew how to read -- forgot how to read within a few generations) disproves your assertion.

@RonJohn: There is a huge amount of popular misunderstanding of the "dark ages".

@R..GitHubSTOPHELPINGICE even now, there are many essentially forgotten arts. In the US mainland at least, skills like blacksmithing, tanning, primitive hunting / gathering and even Industrial Revolution skills have been lost except for a tiny minority who aren't guaranteed to survive the Apocalypse.

But even if your claim were true, that was a time when there was very little written-down technical knowledge (not to mention knowledge for organizing human activity for mutual benefit) that would have been of value to people to read. The degree to which we have documented how to do things in ways that you could recover without any living person still knowing how to do them is completely unlike anything that existed previously in history.

@R..GitHubSTOPHELPINGICE do you really think that a homesteading survivalist-prepper with a wall full of books of chemistry, physics and engineering is going to be able to recreate industrial society? Or even have his grandchildren recreate it? Or will they be working to hard to survive?

@RonJohn: No, "homesteading survivalist preppers" just die. The people who survive are the ones who know how to (and know the value of) working together for mutual benefit, and who have the desire to preserve what humans have developed in this area.

@RonJohn But it's always been the case that only a very small number of people knew those sorts of skills. And while per-capita there's probably fewer people directly employed in such trades, consider that youtube channels focused on those topics collectively get hundreds of millions of views. Humans are very creative when circumstances force the hand, I'm quite confident given the need lots of people could puzzle it out post-apocalypse.