I would start with

"Woman in White"      by       Wilkie Collins

I welcome more recommendations

For convenience I will list all the books in this Reply

                Book Title                                                     Author                                   Recommended By

1. "The Woman in White"                                 Wilkie Collins                             PavanG
2. "Murder on the Orient Express"                   Agatha Christie                          achadamaia (Melody L.) 
3. "The Alienist"                                                  Caleb Carr                                 Catspaw (Sharon W.)
4. "The Hound of the Baskervilles"                Arthur Conan Doyle                   ThreeCats (Lester M.)
5. "A Is for Alibi"                                                   Sue Grafton                                 ThreeCats (Lester M.)
6. "The Beekeeper's Apprentice"                    Laurie R. King                            ThreeCats (Lester M.)
7. "Death by Darjeeling"                                   Laura Childs                               BookShopGal (Sam D.)
8. "The DaVinci Code"                                       Dan Brown                                 poolmysteryreader (arlene L.)
9. "Hush"                                                             Anne Frasier                               crawford (Carol C.)
10. Monkeewrench                                              P. J. Tracy                                   Doughgirl (Lynne J.)
11. Tell No One                                                    Harlan Coben                          cottre26 (Christina C.)
12. The Good Guy                                                Dean Koontz                             junie (June E.)
13. And Then There Were None                        Agatha Christie                         Spuddie (Cheryl R.)
14. Crocodile on the sandbank
15. The Murders in the Rue Morgue
16. Clouds of Witness
17. The Red House Mystery
18. The Innocent
19. 
    

Murder on the Orient Express by Agatha Christie

"The Alienist" by Caleb Carr

Classic: "The Hound of the Baskervilles" by Doyle, since you've already listed The Woman in White.

Modern: Oh, gosh, hard to pick - would be a tie between "A is for Alibi" by Sue Grafton or "The Beekeeper's Apprentice" by Laurie R. King.

But I could probably list 50 must-reads just off the top of my head.

Les

I too agree with "Hound of Baskerville"

Infact this is the book that got me into books......

PavanG

Death by Darjeeling by Laura Childs  would be (and is) tops on my list :)

THE da VINCI code

Hush by Anne Frasier.

Monkeewrench by P.J. Tracy

Tell No One by Harlan Coben.  My favorite!

The Good Guy by Dean Koontz  belongs here!!!  It's riveting and you can't take  your eyes off it!!!!

Hmmm...well, it would probably change depending on when you ask me. But this morning, I'd say And Then There Were None by Agatha Christie.

Cheryl

Here are a few favorites (mostly OLDIES):

Crocodile on the Sandbank by Elizabeth Peters

Murders in the Rue Morgue by Edgar Allen Poe

Clouds of Witness by Dorothy L. Sayers

The Red House Mystery by A.A. Milne

ETA:  If I could only recommend ONE of these it would be "Crocodile on the Sandbank."

The Innocent by Harlan Coben!!!

Something older but still good, Gorky Park by Martin Cruz Smith.  Something newer Faceless Killers by Henning Mankell, introduces Swedish detective in what has become an on-going series. 

I have 2 in the order that I read them: The Innocent by Harlan Coben and The Quickie by James Patterson.

AWESOME!!!!!!!

Any book by Michael Connelly.  But if you are going to read his books, and any in the Harry Bosch series, go back to the beginning ... the book that got me hooked on him ... "Black Echo."

The Thirteenth Tale by Diane Setterfield

Well, I see The Beekeeper's Apprentice has already been nominated, so I'll go with my second choice...A Free Man of Color by Barbara Hambly. The whole series is great.

Bad Luck And Trouble by Lee Child.

I loved this book. I like all the Jack Reachers, but this one is the best so far.

First to Die by James  Patterson

Thanks

Tammy

One of my favorites is Plum Island by Nelson DeMille....It is a mystery but his character is so funny I laughed out loud..Pam

Definitely Elizabeth George's series about Inspector Lynley.  Read them in order, though.  Sometimes I wish that I hadn't read them yet so that I could have the thrill of reading them for the first time again.

Kay

Since Murder On The Orient Express, The Hound of the Baskervilles and DaVinci Code have already been listed, here are other candidates for "toppers" :)

• The Spy Who Came In From The Cold - John LeCarre
• Presumed Innocent - Scott Turow
• Cabinet of Curiosities - Douglas Preston / Lincoln Child
• One Shot - Lee Child
• Rebecca - Daphne Du Maurier
• The Murders in the Rue Morge - Edgar Allan Poe

I could go on since I have not even named some of my favourite authors - Dorothy Sayers, P.D James, Jonathan Kellerman, Jeffery Deaver, Martha Grimes, Elizabeth George, Elizabeth Peters, Ian Rankin, Ruth Rendell and so on. Pretty much anything by these authors is worth reading.

I am a Mike Connely fan as well! Haven't read a single one of his books that I did not like. >^:^>