Something I would like to see would be misc readable books like in DayZ Standalone, I would really like to see the works of HP Lovecraft and the authors that added to the cuthulu mythos. There are a bunch of really good public domain books like Dracula, Mary Shelly's Frankinstien, Don Quixote, Treasure Island, The Art of War, The Call of The Wild, The Time Machine, Moby Dick, The Strange Case of Dr Jekyl & Mr Hyde, The Picture of Dorian Grey I can keep going. Since there is a mental system reading would help alleviate stress.
I have seen suggestions for the ability to learn crafting recipes from books and I would really like to see books and magazines similar to the ones in fallout. Not getting X amount of points when you read it but I would like to see STN created reading material like the patriots cookbook, todays physcian, military surplus review and fixin thing's.
If there are going to be libraries I hope they will not be generic and clones of one another. There are different types of libraries ranging from school to public, each with their own selection of books. I think having different types would be essential to immersion. Say you need to find a book on herbalism. I doubt you would find it inside a library for children ages 6-10. You would need to go to a more populated area with higher risks for your reward.
Also I think finding your desired book should be difficult but not impossible. Make use of the DDC(Dewey Decimal Classification), assigning certain books to certain shelves. Though if you want to make things harder have the books scattered all throughout the building such as in these photo's.
Russian Factory Library:
Detroit - Mark Twain Library:
Detroit - St. Christopher House, Ex-Public Library: