Epistolary: a literary work in the form of letters or documents.
I'm 10,000 words in.
I started out writing "witness" statements for color. They came out so well I kept doing them and at some point I realized I was telling the story that way.
I feel like I have a knack for this format, capturing the voices of the characters. They come out pretty convincing, I think.
It's an interesting technique. On one hand, it's slightly distancing in that it is one step removed from the story. It is a kind of "dear reader" effect in that you are aware that it is after the fact. On the other hand, you can get all the way into the POV of a bunch of characters, which I think cancels out the distancing factor.
It's not the first time I've done it. I was halfway through "Led to the Slaughter" when the Donner Party reached the mountains. I needed to show the suffering, the cold, and the hunger, and I landed on diary entries to show the daily struggle. It worked really well. I also used this technique in "The Darkness You Fear" because the POV character is Virginia Reed, but she wasn't with the Lost Meek Wagon Train, so I had another character's journal telling the story.
Interestingly, I realized that I was currently reading an epistolary novel without having been aware of it: "D.O.D.O." by Neal Stephenson.
I'm kind of winging it so far, quickly using up the research I've done. So far the action is paralleling the Malhuer occupation and the Bundy Ranch standoff. Pretty soon I'll be moving into new territory; a murder and an escalation of action, the 'Juniper Rebellion.'
As long as these characters keep telling the story in an interesting way, I'm going to keep going with this technique. I'm not sure how publishers are going to feel about it, but the books seems to want to be written this way.