There were no texts when I started, just "This page intentionally left blank" updateable binders. We put together user groups, then others put together this thing they called the Internet and we'd use decwrl to get the source, and email to share understanding. Mostly we just built stuff and met maybe at conferences, but shared everything we found or did.
Some went on to write textbooks. I ghostwrote two chapters of Linux Unleashed and started a kernel book so there'd be SOMETHING. ?