Once you get to level 3 of the writing career, your daily task is supposed to be "write books" instead of "read books." However, I had my level 3 writer come home and start reading a book to bring her fun level back up. After a few minutes, I noticed that she had completed 50% of her task to write a book. She still needs to write to get her writing skill up, but it's useful to be able to do this when your sim's fun level is low.