Excellent discussion on why many major novelists (and others) find atheism "useful" over at
Mere Comments. Read the comments too for gems like this:
It's always seemed odd to me that people can profess not to believe in God while making clear, at the same time, a deep personal resentment of Him. I don't believe in Thor - I really, truly "disbelieve" in him - and consequently I cannot imagine being angry at him; I can't wax passionate about Thor's failure to slay the great world-encircling sea-serpent, not for a moment. Yet many who deny the existence of God AND of evil are very quick to launch into a diatribe condemning God for allowing evil, and declare their disbelief in Him in a tone seemingly calculated to try to hurt His feelings!
Joseph Heller, Catch-22