We used to have many many books! I had three bookcases full of books. Some dealing more with concepts and principles. Some just straight up maths in all sorts and forms. Some were reference books, just listing everything there is to know about a language or a piece of hardware for example. Grouped logically and with an index to look up stuff quickly. With the most used ones having post it notes with annotation and as crude bookmarks to look up stuff that was critical and easy to forget, but needed often.
These books were often handed down, generation to generation. A lot of my maths books were from my grandfather, with almost every page having tons of annotations and expansions on the subject. He liked to write his knowledge and thoughts in the books with a pencil. A lot of my shelves also had notebooks full of my own writings about different subjects. Designs, compilations, quick references, etc.
We also had something akin to the internet actually, but it was referred to as the sneakernet. Meaning to transfer information you'd have to walk from one place to another with physical media (floppy disks or even data cassettes or reels if you are real old). It wasn't fast, but there was a lot of excellent content shared around. I remember for example Ralph Brown's interrupt list. Everyone I knew that did software for DOS had a version of that list hanging around. And getting a new version from a friend of a friend was a real treat. There were also libraries and demo programs that were shared around a lot. For Pascal for example there was this SWAG (SourceWare Archive Group) collection that was shared a lot.
When BBS became more popular, people found stuff on that. But it was never a primary source for me, it was always a copy of a disk from a friend of a friend who got it off some mythical BBS somewhere. Books and magazines also often had floppies with them and later CD-ROMs. In the early days not many people had CD drives and CDs were seen as a luxury thing. So books and magazines didn't include the CD, but had a way you could order it for a few bucks and usually it was worth it. Magazines were also much more plentiful at the time with most catering to very niche subjects. I had a magazine back then that released every few months and was nothing but source code listings, deep dives and maths. It wasn't entertainment like magazines became later, it was a way of keeping informed and doing research. Back then we didn't always have hard drives and when we did they weren't as big and very expensive. So having a large library of not just book and magazines, but also floppies and CDs was essential and a mark of a good software developer.
It was a better time I feel like looking back. Everything was much slower. These days we get bombarded with information non stop. Software development has tight deadlines, with new releases days or weeks apart. Back then I would easily spend a week submerged in books and such to fully absorb the information, so I could develop some piece of hardware or software, or both. It would be normal to work on something for months before sharing it with others. And they would take weeks to read all about it before they felt like they could discuss it. It was still hard work, both in effort and complexity, but the brain was allowed to work at its own pace. These days we're just running all the time, because number must go up and will nobody think of the shareholders?
I feel like I'm just an old fart who is becoming a luddite after loving tech my whole life. Not everything was better in the past, but I really don't like the direction tech has taken over the past decade or so.