The story of Job has tons of themes, but the one that I like the best is the way that God answers Job.
Job has lost everything and his friends are telling him that he must have done something to deserve it and if not then God is mean. Job attempts a defense of God, but speaks as if he knows what he is talking about.
God, apparently, looses patience with Job and speaks to him. What I love is how God starts. God lists lots of things that happened at the creation of the world and asks Job where he was when those things happened, or how something came into being. This is God being sarcastic. It doesn't happen very often, but it's kind of fun to read. This underlines one of the themes of the book of Job, and a theme that appears throughout Scripture: If you want to annoy God, speak as if you truly understand him and know what he wants - and if you really want to annoy him speak as if you know what he wants other people to do.