I've made at least a dozen attempts at Thomas Pynchon's World War II novel since I was eighteen, and I've never managed to get far beyond Pirate Prentice's banana breakfast.
Infinite Jest
Of course I've tried to read the novel that made David Foster Wallace famous, since it was published the year I turned eighteen and I still felt obligated to at least try to read and appreciate literary fiction in order to be "serious" about writing. I just never succeeded, most likely for the same reasons I never finished Gravity's Rainbow. It seems my patience for postmodernism is limited.
The Name of the Rose
I know how Umberto Eco's medieval mystery ends, but I don't count it as a book I've successfully read because there are dozens of passages that I just don't have enough Latin to read. It helps a little that I had seen the film adaptation first.
The Hundred Thousand Kingdoms
I'm not sure what stopped me from finishing N. K. Jemisen's novel, or the Inheritance Trilogy of which it's the first. Maybe I got distracted, or perhaps I couldn't bring myself to care about the characters and their struggles. I should probably pick it up again and give it another shot.
The Warded Man
Once I got it into my head that Peter Brett's novel would have worked better as a shonen manga called Tattooed Devil Killer ARLEN I could no longer take the novel seriously or suspend disbelief. That the protagonist basically turned into Batman after a time skip didn't help matters.
Polychrome
Ryk E. Spoor's homage to L. Frank Baum's Oz novels would probably have had more appeal for me if I had actually read Baum's novels as a kid instead of simply watching the film adaptation of The Wizard of Oz when it ran on TV between Thanksgiving and Christmas. Apparently Baum's setting got a lot weirder after Wizard. Spoor's novel assumed prior knowledge of the setting and characters that I lacked and couldn't be bothered to acquire.
Drood
I liked Dan Simmons better when he wrote science fiction. I was also going to say that I liked him better before he became a raving bigot writing unhinged rants about the evils of Islam, but the seeds of that bigotry were latent in the 1980s when he wrote Hyperion. It doesn't help that Drood requires knowledge of Charles Dickens' life and work, particularly his unfinished Mystery of Edwin Drood. I could acquire it, but I was never a fan of Charles Dickens' and I can't be bothered to read his work just so I can make sense of this one novel by Dan Simmons.
The Elfstones of Shannara
I had been told by a few dozen Terry Brooks fans on r/fantasy that Elfstones was a better novel than his first novel, The Sword of Shannara, but the magic just wasn't there for me. Maybe if I head read Elfstones first, and as a child instead of an adult
Byzantium Endures
This is the first of Michael Moorcock's novels of Colonel Pyat, and I've been slogging through it for five years, reading a little more at a time. This isn't a failure on Moorcock's part, but a triumph of characterization. Pyat's dishonesty is the least of his repugnant qualities, and I can only take so much of him at a time. I'm only halfway through Byzantium Endures, and there are three more Pyat novels after that.
I don't think I'll get through them all in my lifetime unless I'm already in so cynical and misanthropic a mood that Pyat's racism, anti-Semitism, nationalism, and misogyny somehow buoy me instead of bringing me down.
If there are books you haven't finished despite a valiant effort, why not blog about them and email me a link? I'm curious.