[kahljorn]

Books were handwritten back in the day so it would take some time and alot of money (they also didn't have high quality paper factories), add to that any translation work involved. Remember alot of the world back in the day was very "illiterate" and most of their knowledge was orally based.
I'd imagine their method of distribution was dependant on who was getting the book. Unless they had some kind of superstition about bringing books onto boats or something. Like Sethomas said most of the books were very expensive so usually they were made for specific reasons so they probably didn't have warehouses full of them.