Fictional literature has always been very interesting in its ability to bring your mind to new places and create characters that may or may not be possible in non-fiction. I think Douglas Thayer does well in his novel, "Will Wonders Never Cease" in depicting common Utah LDS culture through fictional literature.
In Thayer's novel, he depicts a young man's spiritual and physical struggles of being trapped in under an avalanche. It would be hard to use the few non-fictional examples of young men being trapped in an avalanche to illustrate the Latter-day Saint culture as he did. It would be especially difficult to find a young man who lived to tell the tale with such detail as Thayer has.
Generally, I believe that non-fiction has an excellent role in a Mormon setting. We find "testimonies" and lived experiences to be strengthening. Reflecting on this past General Conference, I remember several fictional anecdotes that were used to teach principles in ways that perhaps non-fiction couldn't have. In my opinion, there is great value in both fiction and non-fiction within LDS literature. Thayer could create both a setting and the character that allowed for a very personal interaction with a young man raised in the environment of a Utah LDS home. It may be difficult to reveal the true feelings, concerns, or secrets of a non-fictional character. In this light, fiction could be the best way to bring up sensitive topics with great tact.