SirBlocklips

Some people use the Stendhal mod to copy old books and paste the content into new ones. I suggest that if you're going to do that though, just make sure you discern that whatever character/group you're doing this with is the publisher while mentioning the original author, so it doesn't remove credit from the original author. 

No I mean physically; if you download an old map, vanilla minecraft doesn't have interactable bookshelves, so all books stored on the lotc maps are gone.

You answered your own question then. You don't because they're gone, unless if you see them in a chest.