We believe in God because God has revealed himself to us. How has God revealed himself? He has revealed himself in creation In the original creation, before the fall of man, Adam and Eve enjoyed perfect communion with God and with each other. As a part of this perfect communion with God, they saw him clearly as he had revealed himself in creation. But because of their wicked desires and actions, they “did not glorify Him as God, nor were thankful, but became futile in their thoughts, and their foolish hearts were darkened” (Rom. 1:21). In other words, when Adam and Eve fell, their fall involved more than the loss of original righteousness; it also involved the corruption of their whole nature, including their understanding. Because this is my Fathers world, and continues to be after the Fall, the objective validity of Gods witness to himself in creation remains, but unregenerate man cannot and will not recognize it.
So he has revealed to us but not really because none of us were there when he ''revealed'' to us. A lot of people believe in a lot of different gods which all claim the same thing, I don't see any reason to believe in yours more than allah or zeus.
You are also taking for granted that what a book says it's absolutely true, why?
