The main hall of The Library has a tiled marble floor depicting the Earth as seen from space branching out into fragments of nearly identical Earths, sort of like the CBC logo. Each of the multitude of halls and exhibit rooms branching off from the main hall house not an organized collection but a haphazard compilation of books and book-like things from across the continuum. Because that's what The Library does - it gathers research materials from across the known worlds.
But it's research only, here, no check-out, because if you were to walk out of The Library carrying one of its books in your hands you will not find yourself wherever it is that you came from but rather where the book came from and that can be a very dangerous place. The continuum, you see, may be made up of only Earths, but they are vastly different from each other for the Universe does care about minute probabilities. You will not find another Earth exactly like yours except for traffic lights that are a different color. The continuum is made up entirely of improbabilities - the more unlikely a thing is the better your odds of finding an Earth where it is fact.
And that is why the only one way in and out of The Library is past the Head Librarian's counter. It's not that the Head Librarian is physically intimidating - quite the opposite. If Truman Capote dressed up as Maggie Smith's Dowager Countess for Halloween you'd have a fairly close approximation. But that ageless, sexless authoritarian need only glance over those turquoise horn-rimmed glasses to bring an immediate halt to any and all high jinks for s/he projects an imperial air that few would cross. And, no matter the time or day, the Head Librarian is always at the front counter, patiently stamping through the ever-present stack of new acquisitions.
And that's where the players come in. The players take on the role of "researchers" at The Library, doing the legwork that the Head Librarian cannot do without leaving the counter. For example, this new book about blood-sucking leech men of Earth 2311, is it fiction or non-fiction? Find out. And here's a research card submitted by a patron asking for the circumference of the crown worn by the Queen of the Gorgons on Earth 175-a. Go measure it. And why is this trilogy about the tech-wars of Earth 1337 only two books? Find out where the other book is, or at least how it's supposed to end.
And hurry up, there's a whole other cart of new books that need to be checked in by the end of the day.