Be careful how you characterize God.
When an author writes a story dealing with matters of faith and the Christian doctrine, God is an actual character in the book. Granted, He may not be given lines to speak (more about this temptation below), but God still lives and moves and acts in the story in very specific ways.
If an author is wise and well-catechized, then God moves and acts in the story only in ways that God moves and acts in our own, real, very-much-nonfiction lives. In other words, no matter how fictional the plot and setting of a book may be, God still acts and speaks in that fictional world only as He has revealed He will do so in Scripture: through His Word (Isaiah 55:10-11; Romans 10:17), in Baptism (Acts 2:38-39; Galatians 3:26-27), in His Holy Supper (Matthew 26:26-28), through His Spirit (John 16:8-11; 1 Corinthians 2:10-14), and through the hands of everyone He calls to take care of His people (John 13:14; Ephesians 2:10; 1 Corinthians 12:27).
This means that the author of a story has a responsibility never to give actions or words to God that go beyond His true character as revealed in His Word. God Himself is very much alive and well today, and we authors would be bearing false witness against Him if we have Him, in our books, behave in a way that is contrary to His own Word.
And here is where I think the matter gets tricky for those of us trying to incorporate a living God into a fictional world.
How a Christian character reacts to sin – both to his own sins and to the sins of others – is part of the characterization of God in a story.
In other words, when an author is writing in the point of view (POV) of a baptized Christian, the reader is now living in that character’s head – in his very conscience – and is privy to all that happens there, including the character’s sins of thought, word, and deed. (And sin that character will, for all humans sin.) The author should be careful never to leave the Christian character unaffected by the sin, for the baptized Christian has been given the Spirit of God (Acts 2:38-39). This means that the POV of the Christian must reflect the spiritual conflict (Romans 7:19-25) that inevitably arises when encountering sin, whether it be through revulsion or a stricken conscience or actual repentance or, tragically, a hardened heart.
If an author writes the Christian’s POV without such conflict, the author is, in the end, mischaracterizing God, for God is neither absent nor silent in such conflict. Instead, He promises to convict the Christian of his sin (Romans 3:9-20), to relieve his conscience through the forgiveness of sin (Psalm 30), to provide a way out of every temptation (1 Corinthians 10:13), or to give him over to his sinful desires (Romans 1:18-32). For this reason, and whatever the outcome for the Christian at the end of the conflict, the author must write the conflict lest he mischaracterize the righteousness and salvific intent of God.
For example, if an author, while writing in the POV of a baptized Christian, has the character repeatedly encountering the Word of God while also engaging in louche behavior but never has the character experience any spiritual conflict between the two actions, then the author, inadvertently, characterizes God as having no conflict between the two.
Do you see what I mean?
Now, a quick word about giving God dialogue in a fiction book.
If you are tempted to give the Creator of the universe actual speaking lines in your story, please let me stop you right here: “Long ago, at many times and in many ways, God spoke to our fathers by the prophets, but in these last days He has spoken to us by His Son” (Hebrews 1:1-2 ESV).
Be careful never to give God words that are in conflict with what He has already said through His prophets and His Son. God remains the Authority on all things that have to do with Himself and His creation. If the book you are reading adds to or takes away from what God has already clearly spoken for Himself (Revelation 22:18-19), close the cover and set it down for good.
May God help us to write stories that characterize Him faithfully for the good of His Church.