A scholar’s question - although biggest does not always mean best. My own library, while small, contains many first editions not found in other places. The fact that they are my own books is a mere coincidence - fine volumes, all of them!
There are many great libraries in the world. I have visited all that I was able to gain admittance to in my search for knowledge. Yet not every culture embraces libraries in the same manner.
The elves of Caleda Ablan may possess the finest of magical academia. Asfada is a true gem, and I was once privileged to be permitted admittance to consult a handful of volumes - albeit in the antechambers of the most mundane building and under constant guard.
Aschau also houses many volumes of importance - the colleges across Sonnstahl have long sought to codify knowledge and perfect the teaching of it to the next generation of professors and poets. I’ve always found this instruction by rote a little formulaic for my tastes - learning is to be savoured; a personal experience, not one to be borrowed from another.
However, perhaps surprisingly, I suspect the greatest collections of published works may actually be held in the citadels of the Blasted Plain. It’s not often discussed - few people like their dealings with the Infernal Dwarves to be known - but it’s my belief that they were the first to perfect the printing press, and still produce the finest examples to be found.
I’m not even certain those dwarves value the knowledge they have accumulated in their vaults of stone. I do know that I have often had to trade with Zalaman Tekash to obtain many otherwise impossible to acquire volumes. So much of what passes from East to West leaves a share with the Eastern Dwarves along the way - why not knowledge too? Certainly, they are masters of ascertaining value, in all things.