Other than a set of encyclopedias, a good book is Pocket Ref by Thomas J Glover. It has all sorts of useful information (conversion charts, formulas, reference tables, etc.) You can also look at Desk Ref

Another are any of the Ugly's electrical reference books. Handy to keep with you if you do any electrical work or need to quickly reference some information. The Pocket Ref has pretty much the same stuff but Ugly's is more focused and less broad.

And of course a dictionary and thesaurus are good to have too.

How to Invent Everything: A Survival Guide for the Stranded Time Traveler

It's basically a book on how to DIY various technologies

Sounds like you're talking about an old-school encyclopedia book collection. Like Encyclopedia Britannica. They take up a lot of physical space and sing if the information becomes outdated quickly. But they are a great source for history, geography, science, etc. And you might be able to find them second-hand from an online seller for a relatively reasonable price.

Chemistry, math, physics, optics, metallurgy... The thing that is hard is how your needs for knowledge will change over time and what is accessible to you at each stage.

For general electronics, The Art of Electronics is the goto book. For actually understanding practical stuff, you need to build a knowledge of the industrial revolution and how it evolved. The inventions of James Watt opened up steam. The Bessemer process scaled iron. Large heavy castings drove the potential for large lathes, but lathes are the key to everything. A lathe is capable of cutting a more precise screw than the one used to operate it. That old screw can be replaced with the new, until you achieve your desired precision.

A reference flat is made using two granite stones rubbed together with water in between until the top one creates suction that can lift the other.

Prussian blue and hand scraping are used to make machine flat surfaces.

Automotive suspension components like springs and torsion bars are a good source of cheap tool steel. Engine heads are a good source of casting scrap and quality hardware. Wipers, window motors, and starters are great for building machines. Understanding how to repair and diagnose this stuff is a major skill. Knowing how to make real controlled heat is fundamentally important.

I've never encountered single sources for this stuff.

You can actually download Wikipedia if you have the space for it.

Engineering textbooks and presumably chemistry and medical textbooks. But you then have to be careful to select one that's not massively confusing and a slog to read

I'll probably get vote-murdered for this, because this is unfortunately not a popular opinion for a lot of very justified reasons that I actually mostly agree with, but I'm going to throw this out there anyway, and I hope people hear me out for long enough that you can decide for yourself instead of just kneejerk downvoting.

Imagine if someone created a statistical numerical model that was based on, and could therefore approximately reproduce something close to the cumulative total of all human knowledge ever recorded on the internet which probably represents exabytes of information, but this numerical model was only the size of a few movie files, and you could dump those numbers into a simulator that within some margin of statistical error, reproduced almost any of that information on currently available consumer-level hardware.

If you're not picking up what I'm putting down, I just described open weight LLMs that you can download and run yourself in ollama and other local programs.

They are not intelligences and they do not represent knowledge, because they don't know anything, can't make their own decisions and can never be assumed to be fully accurate representations of anything they have "learned" as they are simply greatly minimized and compressed statistical details about the information already on the internet, but they actually still contain a great deal of information, provided you understand what you're looking at and what it's telling you. The same way demographics can provide a great deal of information about the world without needing to individually review every census document by hand, but never tell the entire story perfectly.

While I agree with the suggestions to get a proper encyclopedia or just download Wikipedia, for a more reliable and trustworthy dataset, I think you're doing yourself a disservice if you dismiss the entire concept of LLMs and vision models just because a few horrific companies are hyping them and overselling them and using them to destroy the world and civilization in disgustingly idiotic ways. That's not the fault of the technologies themselves. They are a tool, a tool that is being widely misused and abused, but it's also a tool that you can use, and you get to decide whether you simply use it wisely, or abuse it, or don't use it at all. It's your call. It's already there. You decide what to do with it. I happen to think it's got some pretty cool features and can do some remarkable things. As long as I'm the only one in charge of deciding how and when it's used. I acknowledge it was plagiarized and collected illegally, and I respect that (as much as I respect any copyright) and I'm not planning to profit from it or use it to pass off other people's work as my own.

But as a hyper-efficient way to store "liberated" information to protect ourselves against the complete enshittification of content and civilization? I don't see the harm. Copyright is not going to matter at that point anyway, the large companies who control the data and the platforms for it have already proven they don't respect it and they're going to be the ones dictating it in the future. They won't even let us have access to our own data, nevermind being able to do anything to prevent them from taking it in the first place. We, the people and authors and artists and musicians and content creators it was designed to protect, now have to protect ourselves, from them, and if that means hiding some machine learning models under my bed for that rainy day, so be it.

Penguin publishes reference “dictionaries” of various subjects, that are more like mini-encyclopedias. I’ve got ones covering mathematics, philosophy, psychology, sociology, and literary theory.

CRC Handbook of Chemistry and Physics better known as the rubber book

Look that up in your Funk and Wagnalls!