I assume you meant to ask, "What is a simile <em>in </em>"The Hands of an Angry God." So, one example is the simile in which the author compares God's wrath to a terrible flood (“The wrath of God is like great waters that are dammed for the present...”).
This is why. The word 'literal' can be defined simply as "face value". For example if some one says I literally haven't slept all night. You would see that this means they have not slept at all.