Recs if you like Diary of a Provincial Lady...

"a novel written as a series of letters between the fictional characters of a narrative. The term is often extended to cover novels that intersperse other kinds of fictional document with the letters, most commonly diary entries and newspaper clippings, and sometimes considered to include novels composed of documents even if they do not include letters at all. More recently, epistolaries may include electronic documents such as recordings and radio, blog posts, and emails."

Katie McGrath recommendations

Behold: yet another of my 2 a.m. deep dives - this time into epistolary literature! The list starts with some of the earliest examples of the form and follows it into the present day, from stories told through letters and diaries to those built from emails, texts, transcripts, and other documents. Whether you’re a longtime fan or completely new to this genre, what interests you most about it?

(A quick note: I put this list together using Wikipedia, blog posts, and Reddit threads. I did my best to keep everything in chronological order, but a few mistakes may have slipped through - it was 2 a.m., after all. If you have any suggestions on what else I should add, I’d love to hear it!)