The authors of the Bible don't seem too interested in proving God's existence. Indeed, the existence of God or a god or a plethora of gods has been assumed in most cultures and societies throughout history. Not all presupposed gods are the same and this is where the Bible comes in...
The authors of the Bible were more or less preoccupied not with proving God's existence but with describing and demonstrating what God is like and how this particular God engages in reality. Whereas, generally speaking, the gods of ancient-worldly conception were manipulable based on how well the subject responded to the god's demands, this God was unconditionally loving and did not play favorites according to merit. Whereas the gods of the ancient world were angry by default, this God was "slow to anger." Whereas other gods were demanding, this God was merciful. Whereas some gods sought after their own ends and met the needs of people only if the people gave something in return, this God was just. Whereas some gods left people without hope, this God was relentlessly faithful to the promise of salvation and renewal. This God was an alternative--an utterly refreshing and deeply loving alternative. One author, years later, would go as far as to say, "God is love."
This alternative sort of God was not the kind of God who observed from the comfort of the heavenly realm. This God, having made the world, loved the world and came to demonstrate the definition of this love though the act of incarnation. This is a God who comes near. And this is a God that sustains and embraces solidarity with the people in most need of salvation (as if we could ascribe a degree to the human need for salvation). This God is Father, Son and Holy Spirit--a God not defined by functional terms but by relational ones--a God who loves us, identifies with us, and suffers with us, guiding us into alignment with justice, love, and goodness. This God frees slaves and forgives murderers, offering life rather than demanding it. This God creates out of love and sacrifices to be with its object.
This is the God who made the world and everything in it... a God who constantly surprises us with a fresh alternative to the conceptions we come up with. A God who meets us where we are and loves us as we are and calls us still to something better. Figuring out what God is like, I believe, is a much greater endeavor than figuring out whether God exists. The former is much more challenging than the latter and much more pressing as well. Who cares if God exists until we've encountered what God is like?
God is merciful, God is good, God is powerful, God is just, God is life-giving, God is creative, God is gracious, God is generous, God is forgiving, God is slow to anger, God is welcoming, God listens, God is restorative, God is peaceful, God is joyful, God is faithful, God is kind, God is gentle, God is patient, God is holy, God is beautiful, GOD IS LOVE!