They were tailored, and surprisingly thorough.
In the last few years I’ve gone through an old lexicon, my grandfather’s book about building cabins, and I studied halfway through an old SolidWorks training book and I’ve been well surprised by how good the quality is. The detail they go into and the quality of illustrations gets very high.
It has left me with a feeling that the past generation were far better at making teaching material, Clippy isn’t the greatest example of that but he was a result of their generation’s thinking about how to teach. We’ve left a lot of it up to YouTube and other solo efforts, and we’ve completely resigned ourselves to accepting that the books required in higher education are more scam than they are instructive.