This idea definitely has some possibilities. Of course, in keeping with the "realistic" theme of craft-making in the game (like steel production), books would have to be made with Middle Ages-level technology.
Just checking Wikipedia, apparently most written material in the Middle Ages was made on vellum, or calfskin parchment, although other animal skins like sheep were commonly used as well (plenty of the animals already in the game would probably do.) The skin must be soaked in a solution of lime (the mineral, not the fruit) and then dried.
http://en.wikipedia.org/wiki/Vellum
You'd also need ink and a quill of some kind. According to the Wiki article on illuminated manuscripts, ink came from a variety of metallic sources, including silver and gold. Minerals were used for other colors (lead for white, malachite for green). In addition, plants were used as well for some colors -- maybe some of the gatherable herbs as well as the non-cave plants available by trade could be used (what color are fisher berries, anyway?)
As for quills, feathers and reeds were used, maybe a rope-red quill would suffice.
http://en.wikipedia.org/wiki/Illuminated_manuscript
Just brain storming, I really like this idea
:cool: