Only Human — Tom Holt

Something is about to go wrong. Very wrong. What do you expect if the Supreme Being decides to get away from it all for a few days, leaving his naturally inquisitive son to look after the cosmic balance of things? A minor hiccup with a human soul and a welding machine soon leads to a violent belch, and before you know it the human condition-not to mention the lemming condition-is tumbling down the slippery slope to chaos.