I had to answer your question to Carolinamom!
I have never enjoyed a book that is all letters, or even many letters spaced through the book. However, I love “The Guernsey Literary and Potato Peel Pie Society”.
I’m not quite through it yet, only a few more chapters to go, but it is highly entertaining. I especially love the questions and answers that go back and forth with great “small” stories in them.
The Guernsey book was well done because it's a work of fiction, and the author created a good number of "voices"...
There were one or 2 minor annoyances for me, but not worth mentioning. I don't really read that much fiction, so this one stood out for me in that context.