Why are there only these 66 books in the Bible? Because God is the ultimate author of the Bible, and He inspired only these 66. All Scripture is breathed out of the mouth of God (Mt 4:4; 2 Tm 3:16). What the human authors wrote did not originate with them but with God, who moved upon them (2 Sm 23:2; 1 Pt 1:20–21).