Mysteries and Secrets...

The Secret of Platform 13 by Eva Ibbotson
The Secret of the Ruby Ring by Yvonne MacGrory
The Black Stallion Mystery by Walter Farley
Peter and the Secret of Rundoon by Dave Barry
The Mystery of the Roman Ransom by Henry Winterfeld

Joe Gould's Secret, by Joseph Mitchell
Lady Audley's Secret, by Mary Elizabeth Braddon
The Secret Orchard of Roger Ackerley, by Diana Petre
Secret Memoirs of the Duc de Roquelaure, by Gaston-Jean-Baptiste Roquelaure
If You Can't Be Free, Be A Mystery : In Search of Billie Holiday, by Farah Jasmine Griffin

The Shakespeare Secret by J.L. Carrell
Secret Prey by John Sandford
The Secret Servant by Daniel Silva
The Secret language of Dreams by David Fontana
McNally's Secret by lawrence Sanders

The Secret History
The Secret Life of Bees
The Secret
The Secret Garden
Secrets and Lies: Digital Security in a Networked World

Harry Potter and the Chamber of Secrets by J.K. Rowling
How Evan Broke His Head and Other Secrets by Garth Stein
Shakespeare's Secret by Elise Broach
Secret Diaries of Miss Miranda Cheever by Julia Quinn
Secret Story of Sonia Rodriguez by Alan Lawrence Sitomer

The Secret Sharer by Joseph Conrad
On Her Majesty's Secret Service by Ian Fleming
The Secret by Julie Garwood
Secrets of a Summer Night by Lisa Kleypas
The Mystery of Edwin Drood by Charles Dickens

The Genesis of Secrecy by Frank Kermode
Why Do Dogs Drink Out of the Toilet?: 101 of the Most Perplexing Questions Answered About Canine Conundrums, Medical Mysteries and Befuddling Behaviors by Marty Becker
The Mystery Method: How to Get Beautiful Women Into Bed by Mystery
Born Round: The Secret History of a Full-time Eater by Frank Bruni
9 Life Altering Lessons: Secrets of the Mystery Schools Unveiled by Kala Ambrose

Mystery of the Silent Friends by Robin Gottlieb
Mystery of the Haunted Mine by Gordon D. Shirreffs
The Mystery of the Empty Room by Augusta Seaman
Mystery at Thunderbolt House by Howard Pease
Two-Minute Mysteries by Donald J. Sobol

I was a sucker for mysteries from Scholastic Books when I was in grade school.

The Mysterious Benedict Society by Trenton Lee Stewart
The Secret Language by Ursula Nordstrom
The Name of this Book is Secret by Pseudonymous Bosch
The Mysterious Island by Jules Verne
Seven for a Secret by Mary Webb

Can You Keep a Secret? by Sophie Kinsella
Secret of the Old Clock by Carolyn Keene
The Secret Agent by Joseph Conrad
Tales of Mystery and Imagination by Edgar Allan Poe
Top Secret Restaurant Recipes by Todd Wilbur

The Secret of NIMH by Robert C. O'Brien
Secret in the Sky by Kenneth Robeson
Secret of the Andes by Ann Nolan Clark
Keepers of the Secret by Barnaby Conrad
Secret Adversary by Agatha Christie

Doctor Grimshawʻs Secret
by Nathaniel Hawthorne*

The Mysteries of Paris by Eugene Sue

The Mysteries of Udolpho by Ann Radcliffe

The Secret History of the World by Mark Booth*

The Secret History by Procopius (have read, hurriedly)

*own these, but havenʻt read them yet; Sueʻs Mysteries of Paris is also on my TBR, for the next time I have a few weeks or months free for reading.

The Red House Mystery by A A Milne
The Mysterious Affair at Styles by Agatha Christie
The Big Bow Mystery by Israel Zangwill
The Mystery of 31 New Inn by R. Austen Freeman
The Mystery of A Hansom Cab by Fergus Hume

The Felony and Mayhem Mystery series

The Marcus Corvinus Mystery Series

The Secret of Luca (Il Segreto di Luca
by Ignazio Silone

The Secret Agent by Joseph Conrad

The Mysterious Island (LʻIle Mysterieuse
by Jules Verne

The Divine Secrets of the Ya-Ya Sisterhood by Rebecca Wells
The Secret Life of Walter Mitty by James Thurber
Secret Song by Catherine Coulter
An Excellent Mystery by Ellis Peters
Secrets of Surrender by Madeline Hunter

The Code Book: The Secret History of Codes and Code-breaking by Simon Singh
The Mystery of Things by A. C. Grayling
Secrets of the Exodus: Did the Pharaohs Write the Bible? by Messod Sabbah
Jude the Obscure by Thomas Hardy
Private Lives by Noel Coward

The Disappearing Floor
by Franklin W. Dixon

O Enigma do Crime no Jardim*
by S.S. Van Dine

O Enigma do Britanic by Jacques Cousteau#

Harry Potter e o Enigma do Principe*

Mysterious Wales by Chris Barber

* The "Mystery/Secret/Enigma syndrome doesnʻt come into the English titles of these, only into the Portuguese.

#29 in his "Aventura" series; probably a strictly metaphorical use of "enigma"; not sure he would want to be in this "mystery" category

Grave Secrets by Kathy Reichs
The Secret History by Donna Tartt
Mystery by Peter Straub
A Caribbean Mystery by Agatha Christie
Why Didn't They Ask Evans by Agatha Christie

The Mysteries Within Sherwin Nuland
The Mysterious West Tony Hillerman
Mysteries of Winterthurn Joyce Carol Oates
Secrets and Surprises Ann Beattie
Mysterious Flame of Queen Loana Umberto Eco

The Secret River by Kate Grenville
The Husband's Secret by Liane Moriarty
The Secret Place by Tana French
The Mysterious Stranger by Mark Twain
A Secret Country: The Hidden Australia by John Pilger

The Mystery at the Chalet School by Elinor M Brent-Dyer
The Crime and Mystery Book by Ian Ousby
Agatha Christie: An English Mystery by Laura Thompson
The Secret History of Wonder Woman by Jill Lepore
The Summer of the Great Secret by Monica Edwards

The Mysteries of Pittsburgh
by Michael Chabon

Mysteries of History by Robert Stewart

The Secret by Rhonda Byrne

The Mysteries of Udolpho
by Ann Radcliffe

"Why Didn't we Know?"
by Ralph Hasson

Promise not to tell by Jennifer McMahon
The Mystery of the Yellow Room by Gaston Leroux
The Secret Woods by Naoki Urasawa
The Inexplicables by Cherie Priest
Las armas secretas (Blow Up) by Julio Cortázar

Mystery oi the Maya by R. A. Montgomery

The Mystery of the Cupboard by Lynn Reid Banks

A Mysterious History by Charlotte Carter

The Case of the Mysterious Behavior of
Some Chemical Elements by Landmark

Secrets of Billy the Kid by George Turner

The Secret Diary of Lizzie Bennet by Bernie Su
The Darkest Secret by Alex Marwood
Every Secret Thing by Laura Lippman
The Secret in their Eyes by Eduardo Sacheri
Secret Daughter: A Novel by Shilpi Somaya Gowda

In the Beginning: First Novels in Mystery Series
by Mary Jean DeMarr

The Mysteries of Pittsburgh by Michael Chabon

The Mysteries of Paris
by Eugene Sue

The Secret Series Complete Collection
by Pseudonymous Bosch

Seven for a Secret by Mary Webb