Yes, 40 years ago I wondered and began to read it. After a two year study, I was amazed to learn what its main message was.
The first book of the Bible, Genesis, shows that rebellion against God's good provisions resulted in humanity being deceived and sinning against God. The rest of the Bible books show that we are all sinners, yet that God's plan to deliver us from our sin is being worked out, supremely in the person of Jesus Christ. The last book of the Bible, Revelation, shows the final outcome for rebels who won't repent, and sinners who have repented. So you could say that the Bible is about the triumph of God's love, justice and mercy over sin, so that God is justified and glorified, as seen most clearly in what Jesus did when He left God's side in heaven to become the man who died on the cross to take away the sin of the world.
The purpose of the Bible is to convey to humanity God's dealings with sinners, how He brings into covenant relationship with Himself those who are His people, to restore the broken fellowship caused in Eden by sin.
Its purpose is to magnify God as the sole God who alone is to be worshipped in the complexity of His Being, which is gradually revealed as time goes by, in the scriptures.
Its purpose is to edify those who would draw close to their God, to instruct and guide them in the way to go, and how to be overcomers in this sinful world.
Its purpose is to give hope and joy here and now to those who learn to trust the God of all grace depicted in the scriptures, plus assurance of Heaven to come.
Its purpose is to confound the wicked and to judge them, as in Psalm 18:25 - "To the faithful you show yourself faithful, to the blameless you show yourself blameless; to the pure you show yourself pure, but to the crooked you show yourself shrewd; you save the humble but bring low those whose eyes are haughty."
It is so awesome, I have been going by it for 40 years, still learning more and more, and blessing God for every word of it.