All sacred texts express our human interpretation of that which we refer to as a higher power, highest consciousness, God, Source or The Universe. There is truth hidden within all sacred text. No matter what sacred text you choose to read you can learn about the nature of the Divine from it and, how our relationship to what we define as God has evolved throughout time.
Well, being skeptical about Christianity doesn't necessarily mean you doubt the existence of God. Maybe you just aren't quite sold on the idea of Creationism because of the overwhelming evidence and hard science that backs evolution. Maybe you believe Jesus existed but aren't quite sure about his whole resurrection story. Or maybe you you’re not certain about the omnipotence of God.