I would personally recommend having a look at the Isle of Kings library.
It is easy to access, large, old, and has a wide variety of books. There you will find literature about the ancients, bonelords, vampires, pirates, gods, elves, dwarfs, the magic longsword and even the Nightmare Knights.
I would also suggest (perhaps a slightly biased opinion on my behalf...) looking around the Fair Plains (Plains of Havoc) for books you can find there. For example in the abandoned monastery, in the dream realm and under the necromant house. There you will find ancient texts which tell the history of the Nightmare Knights. Their connection to tibian lore might be more complex than you imagined...