For every book moved another row of shelves appears. The shelves go up as far as you can see. As long as you can see. The shelves extend back in time to before the written word, chanting and songs can be heard as the shelves give way to painted stone walls and darkness. They extend forward into digital media that has not been invented yet.
Once in a while a node is found. This is a door into another library. The problem is unless it is the world and time you came from, you can't get more than a quarter mile from the node itself. Nodes form where the "weight of words" in a given library exceeds a certain threshold. College archives are prone to such nodes. They have been found in places from temples to tombs.
The books near a node will be related to the node, in that language and of that time. Nodes can be in any place and any time in which such a library exists. A given node will exist throughout time as well. It is possible to find lost books and books that have yet to be written, from your point of view.
The down side is that items in the nodes cannot be removed to another node, unless you own it. As simple as getting a native to give it to you. People own themselves, but without some heavy magic cannot leave the area of the node.
Books in the stacks can be referenced, photographed, or copied. They cannot be removed. Julian has a book copier at a library we are told is in an alternate Earth. A sort of magical replicator. He copies the books he wants and carries the whole through the node, the books of the Stacks evaporate back to the right locations. The copies you can keep.
Located in the "center" it is really hard to say. An opening in the shelves and a round bar with stools. Behind the bar is an Aneilog. Yes the All has a presence here. Sit at the bar and you can get a drink and something to eat. If asked the nice bartender will tell you how to get out. You will also be quizzed as to why you are there. they want your story too.
It is hotly debated by those that hotly debate such things if The Cafe is a real location or an actual node into the All. Is the bartender alive or an aspect in the All? They seem real, and the chicken salad sandwiches relieve hunger in a satisfying way. Real enough for me.
Evidence for the node into the All argument comes from the fact that The Cafe seems unassailable. The various creatures leave it alone. Also, it always has what ever food or drink you ask for. Weird that.
The Stacks are not empty. Various creatures roam them. The most typical are:
A curious red crab-like creature the size of a man's hand. The small creatures are the keepers of the stacks. They know where everything is and where everything goes. If you can communicate with them they are your best friends. They do not speak and even with telepathy they are not loquacious. They can understand the spoken word.
Elminopees want everything in its place. They work together to move displaced books back to their proper shelves. They clean up things that do not belong. This includes despondent graduate students who finally sit down. An Elminopee will pinch their butt and move away, trying to get the person to follow it. The person that does will get home. People standing and moving are assumed to "be in the right place".
A carnivorous saurian with an excessively enormous vocabulary. Recognized for conversing people to extermination, with a remarkable propensity toward Brobdingnagian verbiage.
A Thesaurus resembles a smallish T-tex. It mainly eats ladders absorbing the knowledge within and increasing its vocabulary. They get lonely with no one to talk to, so they run people down to talk to.
The Thesaurus will attempt to corner people and talk them to death. Anyone cornered must make a will save DC equal to their Int score. Failure means you have succumbed and will take 1d4 Wisdom damage. You must continue to make saves. until you either die of the Wisdom damage, or make a save. Those that save can attack and thwart further talking attacks
Wild Academicians have been known to eat the Thesaurus that can't talk fast enough. They have been known to eat the occasional Wild Academician that didn't move fast enough. It's a scholar eat scholar world.
Large slow moving beasts that are phlegmatic in the extreme. They eat the books themselves becoming vast stores of knowledge which they are too bovine to use. It is possible to climb all over ladders and they don't really notice or stop grazing. The biggest danger is being stepped on by one. They are called ladders because you can climb one to reach the upper shelves. They don't really care.
Thesaurus will kill and eat ladders absorbing further vocabulary in the process. Wild Academicians get one once in a while. They are tough and nearly oblivious.
Scholars have been getting lost in here since the written word began. Some have stopped trying to find their way out and live among the stacks. Some are even born here.
Wild Academicians are noted for their unkempt hair and wearing book covers as loin cloths. They carry clubs made from shelves as well as scissors and letter openers stolen from nodes. Rarely they will get the blade from a paper cutter.
Wild Academicians attack to subdue anything that looks even a little like them. Women (rare) are inducted into the tribe. Males (far more common) are quizzed as to their knowledge. Those that pass are inducted into the tribe. Those that fail are consumed by the tribe.
Lost, anything from bemused or scared but OK, to starving and near naked. Desperate for a way out. Most (80%) are male. Once encountered you are their best friend.
Once we were made aware of the place it was easy to find. Pick any college archive or library in the nation. They all tend to have a door to apparently nowhere in the lowest level of their own stacks. No one has the key and no one knows why. Except of course the keepers of such places who to not noise it about. It is not recommended for exploration.
If you do find yourself so lost, sit down. An Elminopee will pinch your butt, follow it. The monsters do react to phasers.
We are still trying to figure out how to use this as a resource. Make no mistake it IS one. Every book ever including the lost ones. The question being how to get them without getting hopelessly lost.