Some novels are rumored to be too dense, arcane, or pretentious to be read in their entirety. Those sorts of novels are my specialty, and I have been emboldened to complete five such novels from beginning to end.
100 Years of Solitude
by Gabriel García Márquez
Over on listverse, list contributor Shane Dayton describes this novel as both overrated and unreadable. I’m afraid I have to strongly disagree. Much like Italo Calvino’s If on a winter’s night a traveler introduced me to possibilities of postmodern metafiction, Solitude introduced me to magical realism.
As I recall, the magical elements were subtly and gradually introduced (or I may be a most unobservant reader). I enjoyed reading what seemed to be a perfectly straight-forward story, but then I realize that some guy has been tied to a tree for quite a long time and wonder if ants should be able to carry a baby. By novel’s end people are flying away in the sky.
Also, I don’t think I have read any author that could paint pictures with words as those rendered by Márquez. (It’s not a novel, but I also read Stephen Hawkings Brief History of Time, which is also mentioned in the listverse article.)
The Bridge of San Luis Rey
by Thornton Wilder
This novel tells the story of five interrelated people that all have a rather unfortunate accident on a bridge in Peru. I heard about this unreadable novel when I was a member of a creative writing listserv. I was reading a CRIT (listserv-speak for critique) of a short story I had submitted. The CRITTER of my story compared it to the "unreadable novel, The Bridge of San Luis Rey". Of course I had to read it, which I did. I turned out to be a quick and fairly enjoyable read. I am not sure what might have made it so unreadable.
Foucault’s Pendulum
by Umberto Eco
My father in-law was always talking about this unreadable book. The author, Umberto Eco, may be better known for writing The Name of the Rose, which was made into a movie that starred Sean Connery and Christian Slater. The premise of the novel is similar to the bestseller, The DaVinci Code. Eventually, he just gave it to me, and I read it. If you hated the The DaVinci Code, you might just like this book. If you liked the The DaVinci Code., than you might find this novel to be one of those thinky stories that are extremely tedious and boring. I profoundly dislike the The DaVinci Code—just wasn’t my cup of tea.
Moby Dick
by Herman Melville

Does anybody read Moby Dick? I am not sure that I perceived all the layers of symbolism the novel is reputed to contain, but it was a fascinating read of a crazed, charismatic captain with a peg leg and top hat. I could tell you about the extended descriptions of rendering whale blubber and the sort of stuff other critics mention, but instead I’ll share another observation. The title of the novel isn’t the only double entendre. In one passage Ishmael absolutely gushes with brotherly love as the crew is elbow deep in oily spermaceti. Squeeze! squeeze! squeeze! all the morning long; I squeezed that sperm till I myself almost melted into it; I squeezed that sperm till a strange sort of insanity came over me; and I found myself unwittingly squeezing my co-laborer’s hands in it, mistaking their hands for the gentle globules. Such an abounding, affectionate, friendly, loving feeling did this avocation beget; that at last I was continually squeezing their hands, and looking up into their eyes sentimentally … Come; let us squeeze hands all around; nay let us all squeeze ourselves into each other; let us squeeze ourselves universally into the very milk and sperm of kindness.
(from chapter 94)
The Tunnel
by William Gass
I would classify this novel as unreadable, and I read it. After reviewing some of the front matter, it would appear that The Tunnel may not be a novel at all. Instead, it is a collection of loosely connected vignettes that appeared as short stories in innumerable literary journals and magazines. Perhaps, Gass had a master document somewhere, and over the years he submitted passages from the master document to these other publications. Sounds unlikely to me, but apparently the book was thirty years in the making. The result was this pointillist tome. You would really have to appreciate the craft of writing to enjoy this novel, which I did, of course, although it took me three years. Seriously, three years. I would, therefore, recommend reading Omensetter's Luck
or In the Heart of the Heart of the Country & Other Stories
as alternatives on your William Gass reading list.