There are various ways we could give a brief outline of the Bible; and being a blog post, this will be brief indeed. But rather than summarise all of the historical events of the Bible, I want to take the approach of looking at the main theme of the whole Bible, which is God's plan of salvation for mankind and how this plan unfolds throughout history.
In the beginning, God created man. The Bible says that God created man “in His image” (Genesis 1:26). We learn what this means in the passages of Genesis as God puts mankind in authority over creation. He is told to name all of the animals, which signifies his dominion over them. And he is told to “work” the garden (Genesis 2:15); to care for God's creation. Essentially, man was to be an “image” of God, imitating God's characteristics of dominion over creation, care for the creation, and so forth. To imitate God, or to share the character of God, is how God intended for mankind to be. This is how God created mankind; “in His image.”
But as we're all familiar with the story; the Devil tempted Adam and Eve to disobey God, and mankind sinned in doing so. The motivation behind this sin demonstrated a distrust of God, and also a lack of love for Him. These are not characteristics of God. That sin, and any sin we do today, always runs contrary to the character of God, and is an act which runs contrary to the way we are supposed to be; to the way God intended us to be. The result of this sin was death. Adam and Eve didn't die physically that moment, but were sentenced to death along with all of their offspring forever more. And from that moment their bodies began to die. Death and decay is something that was introduced into the world by sin. It was never part of God's original creation. In that sense, death is completely unnatural. Nobody is supposed to die; that was not God's intention for mankind.
So man, having put himself in this situation, needed a Saviour. Who could deliver him from death? God, being loving and merciful, promised to provide a means for their redemption. The earliest record of this promise is found in Genesis 3:15...
I will put enmity between you [Satan] and the woman, and between your offspring and her offspring; he shall bruise your head, and you shall bruise his heel. (Genesis 3:15)
This sounds cryptic and confusing, but it does speak of a particular man of the woman's offspring who would essentially restore the right relationship between God and man by destroying the Devil, who is ultimately the god of sinners. The Bible often speaks of people as being either “children of God” or “children of the Devil”. To sin necessarily identifies oneself with the Devil rather than to be imitating God. We are always imitators of the things we worship (See Psalm 115, v8 in particular).
Well, we haven't even moved beyond Genesis yet, but what we've looked at here is the essential foundation for all of the rest of the Bible. The Bible follows the history of the line of Jesus Christ, from Adam, through to Noah, through Abraham, and on. We learn about the formation of the nation of Israel, which is central to the Bible because Jesus Christ was born to an Israelite woman. We follow the line through Ruth and Boaz, and through David and his descendants. We learn a great deal along the way about mankind's desperate need for a Saviour, and of God's character; His continuing grace and mercy, as well as His loving discipline and justice. Israel serves as an example, both for good and for bad, for all humanity for all time. But the central figure of all Scripture, and of all history, is Jesus Christ.
When we get to the New Testament, we read the account of Jesus Christ, the Son of God, who died to save mankind from the curse of sin; death and decay. Jesus understood the predicament we are in, and He had compassion on all people. He loved sinners and He dwelt among them, and showed them the path to their redemption, which was Himself. He grieved over the state of mankind... He saw sickness and death and had compassion, healing the sick and raising the dead. These things are not as God intended creation to be, and Jesus showed that He was here to restore mankind to the way God intended. When we put our faith in Jesus Christ, He begins a transformation in us, transforming us into the image of Christ who was a man not corrupted by sin; a man who was perfectly in the image of God and the way God intended for us all to be. This is really what the whole Bible is about.
And we all, with unveiled face, beholding the glory of the Lord, are being transformed into the same image from one degree of glory to another. For this comes from the Lord who is the Spirit. (2 Corinthians 3:18)