The first thing I noticed was the shelves. Rows and rows of hardwood shelving, stretching beyond what I could see. On the shelves sat endless books.

Evidently this was some sort of library, but it was unlike any library I’d seen. For one thing, the books were all alike, all bound in the same faded Morocco leather. They were all the same thickness and height, so precisely so that you could rest your arm atop any row of them and your skin would contact every single one. The place was awash in ambient light, but I could not discern any obvious light sources; in fact, above me was not a solid ceiling, but a fog that gradually obscured shelves higher than a few dozen. I could not see how high the shelves reached. For another thing, I could not remember entering this library.

I walked down a few rows of shelves. Over the whole library hung a heavy silence, only disturbed by the sound of my footsteps. All the spines of the books were inscribed with flowing text, but I could not make out what language it was in, and the recursively dense loops and squiggles in the script caused me mild distress.

At last my curiosity overcame me and I removed a book at random from the fourth shelf, which was at my eye level. It came loose with a minor cloud of dust. Its cover was just as inscrutable as its spine. Opening it and flipping through its age-brittled pages, I was dismayed but not surprised to find that the text, if you could call it that, consisted of that same infinitely complex calligraphy, whose microscale curlicues seemed to dance in the shifting light—or was it a trick of the eye?

Clearly I was not well anymore. I had to get out of here, whatever here was. I closed the book with a satisfying muffled clap and looked back up at the fourth shelf, but there was no open space for a book.

Disturbing. I was sure I hadn’t moved anywhere since I took the book, but I could not find its spot, nor a trace of a spot where a book may have been removed in the first place.

I heard distant footsteps now, rows of shelves away, but steadily approaching my position. Were they coming for me? Did the library somehow … know that I had taken a book from its carefully manicured rows? Did I disturb the peace? Should I hide? There was nowhere obvious to hide, but I could make a dash through the aisles, kicking off an endless chase down carpet and dust. But I’d be caught anyway. No telling how many staff the library might have, stationed along the aisles, to apprehend me. Best to appear innocent. I held the book with both hands in my best impression of reverence, turned to face the direction of the footsteps with a friendly smile, and waited a terrible forty seconds.

My dreaded comeuppance came in the form of a smartly dressed woman, who said, “Hello, Ms. Colborn. Is there anything I can help you with?”

“No thank you,” I said, shakily. “Actually, sorry, how do you know my name?”

“We’ve been expecting you.”

“We?”

“The librarian has.”

That was … not reassuring at all. At least she seemed uninterested in punishing me for the book that I removed from the shelf. She began to walk me in a direction I could only assume led to the librarian. Her pace was leisurely.

“And who are you?”

“I am a caretaker.”

“For this place?” Not my brightest question, I admit.

“Yes.”

“What is this place?”

“This is the Library of Possibilities. Each book on our shelves, including the one you’re holding, contains a possible world. Every possible world can be found in one of these books.”

“Every possible world? That’s a lot of worlds.”

“Yes. They’re all carefully indexed and cross-referenced in our system.”

“What world is this one?” I held up my book.

“Hard to say, because I am unable to read the script. But its world will likely be similar in world-space to its neighbouring books, and the section whence it came. The librarian will be able to help you with that.”

“I see.”

I did not see at all. In fact, I was beyond bewildered. How could you have literally every possible world enumerated in the books of this library? Didn’t the number of possible worlds increase exponentially with each instant that passed? And what did it even mean for a book to contain a world? All it contained was inscrutable squiggles that threatened to give me headaches if I stared at them too long. I had a mild headache already.

“Forgive me if this sounds rude,” I ventured to the caretaker, “and I think this library is highly interesting, but I have a dinner to get to and was actually just trying to find my way out of here. Could you show me to the exit?”

She frowned. “What do you mean, the exit?”

“Like, back outside. To the streets of, um, whatever city we’re in.”

“City? You must be very confused, we don’t have that.”

This place exists entirely separate from reality. A woman told me that, far back across the mists of memory, in a waiting room. Was this a dream, this strange, unreal location? An illusion?

“Back to reality, then. I need to get back to reality.”

“Which reality? There are many of them.” She gestured down the expanses of shelves. “We are outside them all. If you want to return to the ‘reality’ whence you came, your reality, you’ll first have to locate its book.”

We turned a corner and reached the librarian’s desk.