These are the top 106 books most often marked as "unread" by LibraryThing's users. As usual, bold what you have read, italicize what you started but couldn't finish, and strike through what you couldn't stand. The numbers after each one are the number of LT users who used the tag of that book.

Jonathan Strange & Mr Norrell (149)
Anna Karenina (132)
Crime and punishment (121)
Catch-22 (117)
One hundred years of solitude (115)
Wuthering Heights (110)
The Silmarillion (105)
Life of Pi : a novel (94)
The Name of the Rose (91)
Don Quixote (91)
Moby Dick (86)
Ulysses (84)
Madame Bovary (83)
The Odyssey (84)
Pride and Prejudice (84)
Jane Eyre (80)
A Tale of Two Cities (81)
The brothers Karamazov (80)
Guns, Germs, and Steel: the fates of human societies (79)(not so much that I Couldn’t finish – I just haven’t gotten around to picking it up again)
War and peace (78)
Vanity fair (74)
The time traveler's wife (73)
The Iliad (74)
Emma (73)
The Blind Assassin (73)
The kite runner (71)
Mrs. Dalloway (70)
Great Expectations (70)
American gods (68)
A heartbreaking work of staggering genius (67)
Atlas shrugged (67)
Reading Lolita in Tehran : a memoir in books (66)
Memoirs of a Geisha (66)
Middlesex (66)
Quicksilver (66)
Wicked : the life and times of the wicked witch of the West (65)
The Canterbury tales (64)
The historian : a novel (63)
A portrait of the artist as a young man (63)
Love in the time of cholera (62)
Brave new world (61)
The Fountainhead (61)
Foucault's pendulum (61)
Middlemarch (61)
Frankenstein (60)
The Count of Monte Cristo (60)
Dracula (60)
A clockwork orange (59)
Anansi boys (58)
The once and future king (57)
The grapes of wrath (58)
The poisonwood Bible : a novel (57)
1984 (57)
Angels & demons (56)
The inferno (56)
The satanic verses (55)
Sense and sensibility (55)
The picture of Dorian Gray (55)
Mansfield Park (55)
One flew over the cuckoo's nest (54)
To the lighthouse (54)
Tess of the D'Urbervilles (54)
Oliver Twist (54)
Gulliver's travels (54)
Les misérables (54)
The corrections (53)
The amazing adventures of Kavalier and Clay (52)
The curious incident of the dog in the night-time (52)
Dune (52)
The prince (51)
The sound and the fury (51)
Angela's ashes : a memoir (51)
The god of small things (51)
A people's history of the United States : 1492-present (51)
Cryptonomicon (50)
Neverwhere (50)
A confederacy of dunces (50)
A short history of nearly everything (50)
Dubliners (50)
The unbearable lightness of being(49)
Beloved (49)
Slaughterhouse-five (49)
The scarlet letter (49)
Eats, Shoots & Leaves: The Zero Tolerance Approach to Punctuation (48)
The mists of Avalon (47)
Oryx and Crake : a novel (47)
Collapse : how societies choose to fail or succeed (47)
Cloud atlas (47)
The confusion (46)
Lolita (47)
Persuasion (46)
Northanger abbey (46)
The catcher in the rye (46)
On the road (46)
The hunchback of Notre Dame (45)
Freakonomics : a rogue economist explores the hidden side of everything (45)
Zen and the art of motorcycle maintenance : an inquiry into values (45)
The Aeneid (45)
Watership Down (44)
Gravity's rainbow (44)
The Hobbit (45)
In cold blood : a true account of a multiple murder and its consequences (44)
White teeth (44)
Treasure Island (45)
David Copperfield (44)
The three musketeers (44)

Not bad - 30%+ read, and a couple of these I've listened to Audiobook versions of (Wicked and Freakonomics).