What is the most interesting book you’ve read in which nothing really happens?

What is the most interesting book you've read in which nothing really happens?
What is the most interesting book you’ve read in which nothing really happens?

84 Charing Cross Road by Helene Hanff. There is no action in this book, at all, although history passes by in the background. Just friendship and discussion of books and life in a charming epistolary novel.