Is there any intent to handle the issue of literacy down the road? Within the scope of this update it sounds like everyone will be able to read everything, which makes sense. Throughout history, it was common for largely illiterate groups of people to congregate in taverns (or the like) and have one literate person read a piece aloud. If a significant number of a fortress couldn't read well enough to get a happy thought from a book of poetry, a single literate dwarf could read the poem to his/her peers even if no one is an actual poet, and then everyone would be happier.
I think this would tie in nicely to the "do dwarfs read in their downtime" question, even if all dwarfs remained perfectly literate.This might not make as much sense for "knowledge" books, since people don't typically pick up "Siege engineering for dummies" in their spare time, but it might be a middle-ground between a common "one dwarf reading one book alone" occurrence and a relatively rare "giant festival" event. Similar to small groups of dwarfs dancing in their free time outside of the festival events?
Also, I know that language isn't really an explicit thing right now, and you mentioned getting books translated. Would you ever consider having different languages influence each other and change? Historically, languages like English have been notorious for stealing words from neighbors, and also developing into a massive number of different local dialects (much in the way cultural values flow between different populations). Is this a topic you would ever want to approach?