The Bible is the only book that was...
1) Written over about a fifteen-hundred-year span.
2) Written by more than forty authors from every walk of life, including kings, military leaders, peasants, philosophers, fishermen, tax collectors, poets, musicians, statesmen, scholars, and shepherds.
Moses, a political leader and judge, trained in the universities of Egypt;
David, a king, poet, musician, shepherd, and warrior;
Amos, a herdsman;
Joshua, a military general;
Nehemiah, a cupbearer to a pagan king;
Daniel, a prime minister;
Solomon, a king and philosopher;
Luke, a physician and historian;
Peter, a fisherman;
Matthew, a tax collector;
Paul, a rabbi; and
Mark, Peter's secretary
3) Written in different places:
By Moses in the wilderness, Jeremiah in a dungeon, Daniel on a hillside and in a palace, Paul inside prison walls, Luke while traveling, John while in exile on the isle of Patmos.
4) Written at different times:
David in times of war and sacrifice, Solomon in times of peace and prosperity.
5) Written during different moods:
Some writing from the heights of joy;
Others writing from the depths of sorrow and despair;
Some during times of certainty and conviction;
Others during days of confusion and doubt.
6) Written on three continents:
Asia, Africa, Europe
7) Written in three languages:
Hebrew, the language of the Israelites and practically all of the Old Testament. In 2 Kings 18:26-28 and Nehemiah 13:24, it is called "the language of Judah," and in Isaiah 19:18, "the language of Canaan."
Aramaic, the "common language" of the Near East until the time of Alexander the Great (sixth century B.C. through the fourth century B.C.). (LAlbright, AP, 218) Daniel 2 through 7 and most of Ezra 4 through 7 are in Aramaic, as are occasional statements in the New Testament, most notably Jesus' cry from the cross, "Eli, Eli, lama sabachthani," which means "My God, My God, why have You forsaken Me?" Matthew 27:46 NKJV).
Greek, the language comprising almost all of the New Testament. It was also the international language spoken at the time of Christ, as English is becoming in the modern world.
The Greek script was based on an alphabet presumably borrowed from the Phoenicians and then adapted to the Greek speech sound system and direction of writing. Greek was first written from right to left like the West Semitic language, then in a back-and-forth
pattern, and finally from left to right.
8) Written in a wide variety of literary styles, including:
Poetry, historical narrative, song, romance, didactic treatise, personal correspondence, memoirs, satire, biography, autobiography, law, prophecy, parable, and allegory.
9) The Bible addresses hundreds of controversial subjects, subjects that create opposing opinions when mentioned or discussed. The biblical writers treated hundreds of hot topcis (e.g., marriage, divorce and remarriage, homosexuality, adultery, obedience to authority, truth-telling and lying, character development, parenting, the nature and revelation of God). Yet from Genesis through Revelation these writers addressed them with an amazing degree of harmoney.
10) In spite of its diversity, the Bible presents a single unfolding story. God's redemption of human beings. Norman Geisler and William Nix put it this way. "The 'Paradise Lost' of Genesis becomes the 'Paradise Regained' of Revelation. Whereas the gate to the tree of life is closed in Genesis, it is opened forevermore in Revelation." (Geisler/Nix, GIB'86, 28) The unifying thread is salvation from sin and condemnation to a life of complete transformation and unending bliss in the presence of the one, merciful, holy God.
11) Finally, and most important, among all the people described in the Bible, the leading character throughout is the one, true,living God made known through Jesus Christ.
Consider first the Old Testament. THe Law provides the "foundation for Christ." the historical books show "the preparation" for CHrist, the poetical works aspire to Christ, and the prophecies display an "expectation" of Christ. In the New Testament, the "Gospels...record the historical manifestation of Christ, the Acts relate the propagation of Christ, the Epistles give the interpretation of Him, and in Revelation is found the comsummation of all things in Christ." (Geisler/Nix, GIB'86, 29) From cover to cover, the bible is Christocentric.
Therefore, although the Bible contains many books by many authors, it shows in its continuity that it is also one book.
You can find this information and much more in the book "The New Evidence that Demands a Verdict" Evidence I & II by Josh McDowell