The Bible consists of a collection of sixty-six separate books. These books were chosen, after a bit of haggling, by the Catholic Council of Carthage in 397 A.D.--more than three hundred years after the time of Jesus. This collection is broken into two major sections: The Old Testament, which consists of thirty-nine books, and The New Testament, which consists of twenty-seven books. (Catholic Bibles include an additional twelve books known as the Apocrypha.)
The Old Testament is concerned with the Hebrew God, Yahweh, and purports to be a history of the early Israelites. The New Testament is the work of early Christians and reflects their beliefs about Jesus; it purports to be a history of what Jesus taught and did.
The composition of the various books began in about 1000 B.C. and continued for more than a thousand years. Much oral material was included. This was repeated from father to son, revised over and over again, and then put into written form by various editors. These editors often worked in different locales and in different time periods and were usually unaware of each other. Their work was primarily intended for local use and it is unlikely that any author foresaw that his work would be included in a "Bible."
No original manuscripts exist. There is probably not one book which survives in anything like its original form. There are hundreds of differences between the oldest manuscripts of any one book. These differences indicate that numerous additions and alterations were made to the originals by various copyists and editors.
Many biblical authors are unknown. Where an author has been named, that name has sometimes been selected by pious believers rather than given by the author himself. The four Gospels, Matthew, Mark, Luke, and John, are examples of books which did not carry the names of their actual authors. The present names were assigned long after these four books were written. In spite of what the Gospel authors say, biblical scholars are now almost unanimously agreed that none of the Gospel authors was either a disciple of Jesus or an eyewitness to his ministry.
Although some books of the Bible are traditionally attributed to a single author, many are actually the work of multiple authors. Genesis and John are two examples of multiple authorship.
Many biblical books have the earmarks of fiction. For example, private conversations are often related when no reporter was present. Conversations between God and various individuals are recorded. Prehistoric events are given in great detail. When a story is told by more than one author, there are usually significant differences. Many stories--stories which in their original context are considered even by Christians to be fictional--were borrowed by the biblical authors, adapted for their own purposes, given a historical setting, and then declared to be fact.
The Flood story is an example of this kind of adaptation. Its migration from the earliest known occurrence in Sumeria, around 1600 B.C., from place to place and eventually to the Bible, can be traced historically. Each time the story was used again, it was altered to speak of local gods and heroes.