Solved What's the difference

What's the difference between WRITABLE_BOOK and WRITTEN_BOOK
Currently added a really simple feature to one of my plugins and i keep getting "invalid meta" when opening a book

Code (Text):

    @EventHandler
    public void onEdit(PlayerEditBookEvent event) {
        Player player = event.getPlayer();
        ItemStack book = new ItemStack(Material.WRITTEN_BOOK);
        BookMeta meta = event.getNewBookMeta();
        if(meta.getAuthor() == null) {
            meta.setAuthor(player.getName());
        }
        book.setItemMeta(meta);
        String id = plugin.randomID();
        plugin.addBook(id, book);
        sendMessage(player.getName(), id);
    }

When i then give this saved book to a player it has invalid meta.

 

Thanks for the replies that fixed my issue.