"The Island of the Day Before" by Umberto Eco (1995)
"'Sir,' the libertine replied, 'You cannot present to us ideas that all of us consider true, then demand that we not draw from them the ultimate consequences. I suspect that at this point we no longer need God or His infinity, because we already have enough infinities on all sides reducing us to a shadow that lasts only an instant without return. So, then, I propose banishing all fear, and going - in a body - to the tavern.'"
Umberto Eco, when he wasn't being unbearably pretentious, was a writer and Professor of Semiotics at the University of Bologna. He wrote 7 novels, and countless works of non-fiction.
In The Island of the Day Before, a young Italian nobleman meditates (endlessly) on the meaning of life, time, and other topics while trapped on a boat. About 3/4 of this novel could be described as "trapped on a boat," and the remaining 1/4 could be described as "everything that happened before."
The island mentioned in the title is an island somewhere in the South Pacific, located near the "antipodal meridian," or the 180th parallel of longitude. We might define this antipodal meridian as a kind of International Date Line, where one assumes that the island, sitting as it does on the opposite side of the line, is actually inhabiting a previous day.
All of which makes The Island of the Day Before sound like it could be a fun, lighthearted nautical adventure, but in Eco's hands it becomes a ponderous, often nonsensical diatribe consisting of obsolete philosophical topics. The "everything that happened before" parts of the book are actually pretty good, and offer an interesting window into medieval thought, but the "trapped on a boat" portions contain so little in the way of plot twists, character development, or actual emotion that this book quickly becomes a real chore to get through.
Judged against other pretentious books like Infinite Jest, Gravity's Rainbow, or (in my opinion, the prize-winner) The Flounder, The Island of the Day Before isn't unreadable. It just isn't very interesting. If you liked In the Name of the Rose (as I did), you'll find some redeeming features in it, but if you struggled to get through Foucault's Pendulum (as I did), you'll find The Island of the Day Before even slower going.