While using an unsigned Book and Quill, all other processes in the game stop while the GUI is open. In other words, the game is in "pause". Examples: rain stops falling, entities stop moving, clouds stop moving, no sounds are produced. Closing the GUI "resumes" the environment exactly as it was left.
This issue does not occur with crafting tables, chests, enderchests, or damaged anvils. It appears to specifically be with Books and Quills.
Adrian Östergård
On second thought, this could be an intended feature for single player.