The Shelves is a city on a book shelf.
Civilization is limited to the top two-thirds of the shelves. No one seems to know exactly what goes on in the lower shelves, but it is considered highly dangerous and chaotic- perhaps even more so than the rauckus Tablelands (see below!)
Most shelf-dwellers live in what is called a cubby. A cubby is a space not visible when viewing The Shelves from the outside. Essentially, it is an "imaginary space" which action figures are capable of viewing and entering but larger humans are not. A cubby is usually about the size of a small studio apartment and contains a toilet, a hygene unit, a cooking unit and a bed. Cubbys are also outfitted with a television and a loud speaker.
Akin to the "imaginary space" that is the cubby are the various "imaginary ladders" and "imaginary doors" which can be found around The Shelves. "Imaginary doors" between shelves are generally found at the ends of each shelf. There are also "imaginary doors" in certain barriers, such as books. "Imaginary ladders" are more half-hazard in their placement, but there is always one somewhere leading up or down from a particular shelf.
The standard currency on The Shelves is the corner. Since a corner is a corner page torn from a book, and its value is based on its page number, making change can be difficult (there are as many ones as there are tens in circulation.) Thus, barter is more common than in many capital-based systems. A corner may or may not be roughly equivalent to a dollar.
Almost everything comes from books. Building material (including substances which are not paper,) energy, and knowledge all come from books. Books, then, are similar to an "imaginary ladder."
The process by which substances like various metals and gems, as well as energy, is extracted from books is not known to the general populace, and so it shall not be discussed here. However, it is known that the extraction of these things depletes the book in some way, potentially making it useless.
Knowledge may be harvested from a book by anyone willing to take the time to do so. To learn, a shelf-dweller with a sufficient mental capacity (only so much information can fit into a plastic head) crawls into a book ("imaginary space") for an extended period of time and, later, crawls out with a new skill, some previously unknown knowledge, or valuable life experience. This can also be done for pleasure as every book contains its own booky world. Using a book in this way is not known to deplete the book.
There are many different ideas about where The Shelves came from, the nature of books, and why the Shelf-Dwellers are here. Your character may subscribe to one of these, or they may not feel they know or care. The choice is yours. Below is a bit about the most common, or most visible, rather, belief.
The Church of the Semi-Infinite Light is both a visible and potent belief structure in part because they hold a large chunk of real-estate; The Temple of the Semi-Infinite Light. The Church, among other things, holds "services" at the Temple, at which Mystic Mogar (High-Prism of the Semi-Infinite Light) informs the public about the Semi-Infinite Light and demonstrates its power. All are welcome to attend and many do.
And many do not. There are rumors of another, competing religion meeting somewhere clandestinely among The Shelves. Whether this religion exists or not, and what beliefs it holds to be true, is not known, but it can be fun to think about.
Other than this hypothetical secret cult and The Church of the Semi-Infinite Light, there are no other established religions on The Shelves.