The God Proof is a novel, but it is about a real proof claimed by Kurt Gödel, Einstein's closest friend. Many people have tried to prove God's existence. You can certainly doubt that it's possible. What you can't question is that if anyone could do it, Gödel could. Time magazine called Gödel the greatest mathematician of the last century. Oppenheimer, scientific director of the project that built the atomic bomb, called Gödel "the greatest logician since Aristotle." Gödel earned his reputation with airtight proofs of unexpected results.
The shy Gödel feared ridicule. He probably told Einstein about his God Proof, but he told nobody else until 1970, and he never went public. After Gödel's death, his papers were found in careful order. We know what is missing and what is not. Everything was there, with two exceptions: the notebooks with his work on the God Proof.