I love reading epistolary novels — once in a while, it’s really quite refreshing to read narrative that’s broken down into pieces of interesting text (e.g. letters, reports, memos, etc.) rather than plod through long chapters. There’s also the wicked fun of reading other people’s correspondence and attempting to piece together a story based on them.
My favorite epistolary novels include Dracula by Bram Stoker, Griffin and Sabine by Nick Bantock, Daddy Long Legs by Jean Webster, The Historian by Elizabeth Kostova, and even Meg Cabot’s Every Boy’s Got One. I read a couple more recently: Up the Down Staircase by Bel Kaufman, and Ella Minnow Pea by Mark Dunn.