Eschatological fantasy from Bear (Quantico, 2007, etc.).
One hundred trillion years from now, an entity known as the Typhon, or Chaos—the distinction isn't clear—lazily absorbs what remains of the universe; only the city Kalpa survives, watched over by the near-omniscient but distracted Librarian. In a Seattle-like city in a time similar to our own, Ginny Carol flees from sinister pursuers and takes refuge in a vast warehouse full of books, some readable, most not, presided over by enigmatic bibliophile Conan Arthur Bidewell. Ginny carries a mysterious jewel called a sum-runner; she dreams of the remote future, of a city named Kalpa and a young woman explorer named Tiadba. Soon, Jack Rohmer arrives at the warehouse; he too carries a jewel and dreams of Kalpa, and of a young warrior named Jebrassy. Ginny and Jack have the ability to move through alternate realities, but both are finding their choices increasingly restricted. In Kalpa, meanwhile, the Librarian creates Tiadba and Jebrassy out of primordial matter, gives them some companions and sends them off into Chaos. More people arrive at the warehouse: some witches, some cats, Daniel Patrick Iremonk—he can cross alternate worlds by moving from body to body, ejecting the current occupants as he goes—with his evil nemesis, Max Glaucous, sometime agent of the Chalk Princess. Yes, it really is that affectless and unintelligible.
Somehow, all this will save the universe, or maybe start a new one, but trillions of—no, wait—hundreds of pages later, you still won't care.