These are the top 106 books most often marked as "unread" by LibraryThing's users as of 9/30/07. As usual, bold what you have read, italicise what you started but couldn't finish, and strike through what you couldn't stand.
Jonathan Strange & Mr Norrell (This is sitting on my bookshelf waiting for me)
Anna Karenina
Crime and punishment
Catch-22
One hundred years of solitude
Wuthering Heights
The Silmarillion (In three days. On a bet.)
Life of Pi : a novel
The name of the rose
Don Quixote
Moby Dick
Ulysses
Madame Bovary
The Odyssey
Pride and prejudice
Jane Eyre
A tale of two cities
The brothers Karamazov
Guns, Germs, and Steel: the fates of human societies (Don't have it, want to read it...eventually)
War and peace
Vanity fair
The time traveler's wife
The Iliad (If I've read parts in latin, does that count double?)
Emma
The Blind Assassin
The kite runner (It's borrowed, on my shelf, and staring at me. I have no desire to read it).
Mrs. Dalloway
Great expectations
American gods
A heartbreaking work of staggering genius
Atlas shrugged
Reading Lolita in Tehran : a memoir in books
Memoirs of a Geisha
Middlesex
Quicksilver
Wicked : the life and times of the wicked witch of the West
The Canterbury tales (Not that I couldn't finish...I just didn't).
The historian : a novel
A portrait of the artist as a young man
Love in the time of cholera
Brave new world
The Fountainhead
Foucault's pendulum
Middlemarch
Frankenstein
The Count of Monte Cristo
Dracula
A clockwork orange
Anansi boys
The once and future king
The grapes of wrath
The poisonwood Bible : a novel
1984
Angels and demons
The Inferno (The book was someone else's, see, so I really couldn't finish)
The Satanic Verses
Sense and sensibility
The Picture of Dorian Gray
Mansfield Park
One Flew Over the Cuckoo's Nest
To the lighthouse
Tess of the D'Urbervilles
Oliver Twist
Gulliver's travels
Les misérables
The Corrections
The amazing adventures of Kavalier and Clay
The curious incident of the dog in the night-time
Dune (Up for a reread. SO MUCH I didn't get in middleschool).
The prince
The sound and the fury
Angela's ashes : a memoir
The god of small things (It is difficult to describe the myriad ways I loathed this book)
A people's history of the United States : 1492-present
Cryptonomicon
Neverwhere
A confederacy of dunces
A short history of nearly everything
Dubliners
The unbearable lightness of being
Beloved
Slaughterhouse-five
The scarlet letter
Eats, Shoots & Leaves: The Zero Tolerance Approach to Punctuation
The mists of Avalon
Oryx and Crake : a novel
Collapse : how societies choose to fail or succeed
Cloud atlas
The Confusion
Lolita
Persuasion
Northanger abbey
The catcher in the rye
On the road
The hunchback of Notre Dame
Freakonomics : a rogue economist explores the hidden side of everything
Zen and the art of motorcycle maintenance : an inquiry into values
The Aeneid (What I said about the illiad and latin? Yeah, that).
Watership Down
Gravity's rainbow
The Hobbit
In Cold Blood : a true account of a multiple murder and its consequences
White teeth
Treasure Island
David Copperfield
The three musketeers
This is taken from LibraryThing data. I'm a huge fan of LibraryThing, but there are some points to consider in their lists...
1. Almost always, a person OWNS the book they tag (unless they've set up a library for want-to-reads or something). So, this list represents books that people bought or were given but haven't read. Many of them are probably among the most read books, period. Otherwise it'd be a list of things like your Aunt's Lulu-published gerbil raising treatise.
2. This is LibraryThing users. If you think that doesn't skew any list, consider how likely most people are to want to catalogue their entire book collection...for fun. I KNOW - I'M ONE. I bet this accounts for all the Neal Stephenson/Neil Gaiman among the Classics and Book Club selections.
And lastly, WHY are "Book Club" type books ALWAYS so goddamn depressing? I SERIOUSLY don't get this.