Most writers eventually find themselves writing about some kind of text. A lover might leave a note that changes the course of a novel, or a character may complain about a major plot event in his diary. Some writers take things a little further by using an epistolary structure to frame an entire narrative.
Epistolary stories are told entirely or in large part through texts. Traditionally, they’re told through letters, but modern works like Mark Z. Danielewski’s House of Leaves and Joseph Fink’s Welcome to Night Vale have used everything from advertisements to elaborate fake scholarly articles to tell their stories. Generally speaking, these narratives don’t break the fourth wall – they get their appeal from the way they communicate with an audience as fictional as they are.
The thing about epistolary narratives – and this can make them either excellent or wildly inappropriate for your story – is that they ask you to manage a very complex relationship. The narrator is communicating with an audience which exists within the universe you’ve created for the story, but the readers who pick up your book in real life are the ones who really need the information. You need to carefully and subtly work in world-building elements when you write an epistolary narrative. The narrator will need to spend some time talking about how people in your story go about their day, and their linguistic choices need to represent their background and their personalities.
A lot of writers don’t write many stories in epistolary form, but there are some who find it’s the most effective way to tell about a story. If you want to challenge your readers, some form of epistolary narrative can certainly help you provide an unusual and colorful narrative. However, writers should be extra conscious of clarity when using this intimate narrative form.