If the Bible was only a book of good advice, or a collection of ideas about religion that people had thought up over the centuries - then you'd be right: There wouldn't be much reason to base our lives on it.
But the Bible is far more than that! The Bible isn't just another human book; it is God's Word, given to us to teach us about God and our need of Him. To put it another way, in it God reveals Himself to us - and that sets it apart from every other book ever written. As the Bible says, "Prophecy never had its origin in the will of man, but men spoke from God as they were carried along by the Holy Spirit" (2 Peter 1:21).
This is why the Bible is timeless, and speaks to our generation just as powerfully as it did to people a hundred generations ago. After all, God does not change, and neither does human nature. Nor does God's plan of salvation in Christ change, because we need Him just as much today as people ever did. Christ is the center of the Bible's story, and "Jesus Christ is the same yesterday and today and forever" (Hebrews 13:8).
I realize you may not believe right now that the Bible is God's Word - but I urge you to discover it for yourself. Begin reading (perhaps in one of the Gospels, such as John), and ask God to show you if it's true. Your life will never be the same.