I thought this was an insightful point with regard to the challenge of using non-fiction characters in a fictional book:
When you deal with non-fictional characters, you inevitably open yourself up to criticism.You can read the whole review here.
Let’s say you meet an author who wants to use your grandparents as the main characters in a novel. The author tells you that the narrative will be fictional, but that your grandparents will have the starring roles. Sounds great! you think.
But when the manuscript arrives in your hands, you discover that the story does not accurately represent the personalities of your grandparents. The relationship between them is all wrong too. Grandma berates Grandpa. Early on, they run off and elope (which is totally out of character). At one point, they contemplate divorce.
When you complain, the author responds, “Remember? I told you it would be fictional.”
“Yes,” you say, somewhat exasperated, “I knew the story would be fictional, but I thought you would get my grandparents right. The grandparents in your story aren’t anything like my grandparents.”
“Who cares?” the author responds. “It’s a work of fiction.”
“Well, I care,” you say, “because people will put down this book thinking that my grandparents were like the way you portrayed them.”
My biggest problem with The Shack is its portrayal of God. I understand that the book is a work of fiction, not a theological treatise, and therefore should be treated as fiction. But the main characters are the Father, Son, and Holy Spirit. These are actual Persons. To portray God in a manner inconsistent with his revelation to us in Scripture (and primarily in Jesus) is to misrepresent living Persons.
When people put down The Shack, they will not have a better understanding of the Trinity (despite the glowing blurbs on the back cover). They will probably have a more distorted view of God in three Persons.