Director of Research would be a noble position which would mandate the research of certain topics, as elected by the scholars/appointed by the crown/player.
Rather than an unfulfilling and gamey "tech tree", or research that consists entirely of historical or otherwise non-interactive work (astronomy, levers, etc.), scholars could also compile scientific data on things like the specific weights, volumes, and abilities of forgotten beasts, experiments, undead, wildlife, and the appearance and behavior of living figures i.e. vampires and warmongers, based off of the accounts of citizens, soldiers, liasons, and dedicated research missions. This data would be directly availible to the player by examining books like "On [Hist fig/FB]" and "Fauna and Haunted Weather of [biome]". In general, scholars could retrieve legends info that is more relevant to the fort than odd historical events.
Maps could also be created, again using legends data.
Caravans could value books based off of their content (guides to territories they're interested in, research on animals/people that align w their spheres, etc.)
Manuals could be written (by guilds?) describing certain processes and added to workshops to improve learning rates. Certain jobs (gem-cutting, strand extraction, elven growing magic, animal training, etc) might be prohibitively difficult/expensive to learn without a manual and/or instructor, inciting a need to send dwarves away to college/host a college of your own.
Imagine getting lucky with a voted director who likes the forgotten beast sphere so you can be prepared, or having to magma a director whose only interest is the local herbs.
Caravans would value books based on their content relative to their civs knowledge corpus and spheres. Elves would love a scroll on the climate of a prospective territory but reject a manual on growing methods, etc.
The crown could give grants/pay premiums/threaten the fort to keep certain knowledge inside the civ like FB info, etc. (or perhaps keep secret the appearance of an ancient vampire who disappeared shortly before the king's succession?)
Research could play a role in the outcomes of hist gen battles. Art/poetry could shift the values of a whole civ.
Demonology/Angelology would be an interesting field.