I can't remember the title or author in which a new super computer is built and it answers the question...
Is there a god?
There is now.
"Thank you," said Dwar Reyn. "It shall be a question that no single
cybernetics machine has been able to answer."
He turned to face the machine. "Is there a God?"
The mighty voice answered without hesitation, without the clicking of
"Yes, now there is a God."
I think that would have to be the computer in Isaac Asimov's The Last Question, who, upon being asked The Last Question
Creates the universe.
Strictly speaking, that is a short-story and not a novel, though.