Pratchett's L-Space: physics and libraries intersect...

"L-Space" is discussed in several books in several different appearances of The Librarian (now an orangutan, post-magic-accident). The DiscWorld Companion summarizes the concept thusly:
"Even big collections of ordinary books distort space and time, as can readily be proved by anyone who has been around a really old-fashioned second-hand bookshop, one of those that has more staircases than storeys and those rows of shelves that end in little doors that are surely too small for a full sized human to enter."