The Bible is a unique collection of writings. In fact, there is nothing like it in all the world. In a period of over fifteen hundred years, and written in three distinct languages (Hebrew, Aramaic, and Greek) on three separate continents (Africa, Asia, and Europe), at least forty human writers from vastly differing fields, perspectives, and backgrounds wrote under the direction of the Holy Spirit in putting together the sixty-six books of the Bible.
The people who wrote it were shepherds, fishermen, and military men. There were kings, a prime minister, and a royal cupbearer. There was even a doctor, a tax collector, and a tentmaker among so many other people from different walks of life. They wrote in a number of unusual circumstances, as varied as being in a prison or a palace.
As the Bible was written over such a lengthy span of time, most of the writers did not personally know one another, nor live in the same eras. The Old Testament writers would also have no way of accessing the writings of the New Testament. Although most of the writers did not know the other writers, they all still wrote a story that has complete harmony and continuity from beginning to end. This miraculous feature of Scripture is a testament to the fact that the Bible is what it claims to be: the very Word of God.
Because the Bible is written by a variety of people, God used their personalities, strengths, experiences, backgrounds, circumstances, and abilities to bring forth His message. This is why the Bible contains a great number of different literary styles and approaches. It is a collection of historical narratives, commandments, prophecies, letters, sermons, songs, prayer, praise, genealogies, warnings, poetry, proverbs, parables, and practical sayings.
The writers of the various books also cover many different topics, including such subjects as the nature of God, the creation and purpose of mankind, and the coming of the Promised Messiah.
With such a diverse range of writers, places, languages, time periods, circumstances, styles, and subjects, one would expect any book of such magnitude to be a somewhat incoherent mishmash of thoughts and ideas. And quite rightly so.
Yet it isn’t that way with the Bible. The Bible isn’t disjointed, it doesn’t contradict itself. It is one unified book that tells a harmonious narrative from start to finish.
The reason for that is because God Himself is the source and inspiration of all Scripture (2 Tim. 3:16). That fact is the only logical explanation for how the Bible came to be, that God superintended it all. In putting together the Bible the way He did, God unfolded His story over a vast period of time, transcending the bounds of time and space to reveal Himself as being the one true God. Only God could have accomplished such a task.
The Bible does indeed have many different writers, but there is only one Author.
For further reading:
What is the Bible? http://carm.org/what-bible
When was the Bible written, and who wrote it? http://carm.org/when-was-bible-written-and-who-wrote-it
If the Bible is written by sinful people, how can we trust it? http://carm.org/bible-sinful-written-by-people-can-we-trust-it
Inerrancy and inspiration of the Bible http://carm.org/inerrancy-and-inspiration-bible