Letters and Diaries

The Screwtape Letters by C.S. Lewis
Africa in my Blood: An Autobiography in Letters: The Early Years by Jane Goodall
The Letters of Abelard and Heloise by Peter Abelard
Diary of a Nobody by George Grossmith
Diary of a Madman and Other Stories by Nikolai Gogol

The Diary of a Country Parson by James Woodforde
Kilvert's Diary by Francis Kilvert
Jenny - My Diary by Yorick Blumenfield
The Smoking Diaries by Simon Gray
Mrs Weber's Diary by Posy Simmons

The Chicago diaries of John M. Wing, 1865-1866, by Robert Wiliams (ed.)
Dieci lettere private, by Niccolò Machiavelli
Diary of an Erotic Life, by Frank Wedekind
Letters of Mistress Henley published by her friend, by Isabelle De Charriere

and a twofer:
A Very Private Eye: an Autobiography in Diaries and Letters, by Barbara Pym

Diary of a Wimpy Kid by Jeff Kinney
Dear Mrs. Larue: Letters From Obedience School by Mark Teague
The Absolutely True Diary of a Part-time Indian by Sherman Alexie
Letters From Rifka by Karen Hesse
Diary of a Young Girl by Anne Frank

The Henry Root Letters by Henry Root
College Life. letters by Thomas Whyteread
Letters from a Self-made Merchant to his Son by George Henry Lorimer
The Cat that could open the Fridge: A Curmudgeon's Guide to Christmas Round Robin Letters by Simon Hoggart
Three Letters from the Andes by Patrick Leigh Fermor

Letters to Malcolm, Chiefly on Prayer by C S Lewis
The Lyttelton-Hart-Davis Letters, ed Rupert Hart-Davis (can I claim this as 6, since there were actually 6 volumes?)
Letters to his Son, by Lord Chesterfield
The Woman in White by Wilkie Collins
Letters from Iceland, by W H Auden and Louis MacNeice

Letters by John Barth

Letters and Diaries, 1930-1964
by Harold Nicolson

The Diary of a Forty-niner by Chauncey Canfield

Letters from Skye by Jessica Brockmole

Letters and Diary of Allan Seeger by Allan Seeger

The Country Diary of an Edwardian Lady
3,000 Mile Garden: An Exchange of Letters
Pages from a Scullion's Diary
Mary Chesnut's Civil War
Dear Juliette

Princess Diaries
Daddy-Long-Legs
The Diary of Lady Murasaki
Love Letter
The Scarlet Letter

The Clue in the Diary by Carolyn Keene
Diary of a Worm by Doreen Cronin
Diary of Samuel Pepys by Samuel Pepys
Letters From the Earth by Mark Twain
The Jolly Postman; Or Other People's Letters by Janet Ahlberg

These is My Words: The Diary of Sarah Agnes Prine by Nancy E. Turner
The Rossetti Letter by Christi Phillips
This is Going to Hurt: Secret Diaries of a Junior Doctor by Adam Kay
Dear Diary, I'm Dead by R. L. Stine
Sam's Letters to Jennifer by James Patterson

A Letter from Israel by Papas

The Palace Diaries: the True Story of Life at the
Palace...Prince Charles ed. by Sarah

The Hitler Diaries: Fakes that Fooled the World
by Charles Hamilton

People in a Diary: a Memoir by S. N. Behrman

Hide that Can: a Photographic Diary: the Men of Arlington House
by Deirdre O'Callaghan