Fire represents the cleansing of humanity, and destruction in that society. Fire destroyed books, people's personal property, and people themselves, and represented a new beginning for people.
In mythology, when a phoenix is reaches the end of it's life, it will create a fire and burn itself. Then, the phoenix will be reborn out of the ashes. The phoenix represents the earth, and how humanity is constantly building itself up, and then destroying itself through war, and having to rebuild again.
Books represent knowledge and wisdom in that society, and the independence from technology. The books also can represent "regressive tendencies" in the society.