It really bothers me that we can't write in the books that we make. I wonder if the 1.8 update will allow us to write in books? It would improve mapping and would allow players to make logs and inventories in the game.
Actually, now that you mention maps and books in the same contexts, I think a practical application for books might simply be map storage. Instead of having writable books purely in the interest of backstory, they could be used to store maps of different areas of a player's Minecraft world. This is assuming of course that we don't get maps place-able on walls first