Reintroducing guilds into the game, as your fortress becomes more known for a certain thing would probably be more interesting to the player (as guilds set up shop as politically powerful portions of your own fortress) than simply having a few books perform the same function.
I don't think it's mutually exclusive. You could get some basic info from books and require guilds later, for higher levels. All in accord with the "more complexity and options further down the road" philosophy.
Other then that, what do you think about the general idea, Kohaku?
I would think that guilds wouldn't want those books getting out of their own hands.
Maybe having unsanctioned books would anger the guild, which would have its own diplomacy functions to contend with.
In the old 2d version, guilds would set up shop in your fortress, but only about 5 would actually come, no matter how large your fortress was, and you needed at least 3 or 4 of a given labor to have a guild show up.
If we had only one carpenter, for example, we might need some sort of intermediate step, like having a guild rep occasionally come by the tavern if you have one, and being willing to give a temporary tutoring or allowing the temporary borrowing of a sanctioned guild book.
This also gets tied up with the whole notion of skill levels, and what they mean, though.
If I was capped at rank 10 masons, and only very rarely got masterpiece floodgates, I wouldn't really care very much.
Realistically, I would want a craftsman who doesn't mood to eventually learn to be a little bit better over a much longer period of time (like a year a rank) depending on if they have something like a "strives for excellence" or "open-minded about new ideas" trait or something, as well.
I've also had some of these same arguments that became very heated in the past about how, to a certain extent, just making a
working drawbridge triggered by a properly-calibrated pressure plate is a much greater feat that requires all the engineering knowledge you will need on the subject. Higher skill simply results in making a "higher quality" version of the same working machinery.
To an extent, skills as they stand more represent the sort of refinement that comes from a steady hand and training (a dabbling mason still makes a table, it's just that the legendary mason makes a much prettier table with smoother edges and design flourishes) than it repesents the actual acquisition of knowledge of how to build an object at all.
Going into the whole argument of having certain items we can't build until we see a book on the subject, or import a specific kind of machinery or something is generally something that creates a lot of strife and little consensus.