http://wiki.themanaworld.org/Tulimshar
The library would contain information about general gameplay, world and local history, geography and a little about the most common monsters. Depending on the skill system, some "skill books" for common skills and basic recipes could be also found. The information would be in form of readable books: adventurers' diaries, old studies, storybooks, recipe books and so on. Hints for quests could be hidden in the stories.
There could be an inner area needing to complete a quest to gain access to. Inside would be rarer books and prehaps an alchemy or magic shop or an npc selling those items.
Because Tulimshar's history in the wiki is only brief, I'll make some suggestions considering the library.
- The library is a monument built for the magician who designed and lead the casting of the soil protection spell.
- It is not built in the palace area, instead "near the people". Maybe because some hostilities between the magician and the senate(?).
- The magician is buried in the library, not in the royal tombs, because of the hostilities.
- There is a statue of the magician in the main hall.
- There must be absolute silence in the library!

Please send more suggestions and comments about the whole idea.
-- Nafti