The Bible is not a simple book written by a single author over a weekend. It is actually an incredibly complex library of 66 distinct books, written over a span of about 1,500 years, by more than 40 different human authors across three continents (Asia, Africa, and Europe) in three languages (Hebrew, Aramaic, and Greek).
The human authors came from wildly different backgrounds. They included kings (David and Solomon), prophets (Isaiah and Ezekiel), a physician (Luke), fishermen (Peter and John), a tax collector (Matthew), and a former Pharisee (Paul).
However, while there are many human authors, Christianity teaches that there is only one divine Author. This concept is called 'Divine Inspiration.'
2 Timothy 3:16 states that 'All Scripture is God-breathed.' This doesn't mean God treated the authors like mindless typewriters, dictating every single word while they sat in a trance. Instead, God's Holy Spirit worked through the unique personalities, vocabularies, and cultural contexts of each writer to ensure that exactly what He wanted communicated was written down without error.
The ultimate proof of the Bible's divine authorship is its astonishing unity. Despite being written across thousands of years by diverse people who never met, the entire library tells one cohesive, consistent story of redemption pointing directly to Jesus Christ.