Why the 100 year mark? I presume you haven’t been alive and reading adult literature for 100 years. There are far newer works that have entered the cultural zeitgeist to the point that it’s hard not to be spoiled just by living in the world (think Harry Potter or Twilight). There are far older works that most people don’t know—I doubt the average person on the street could tell you the major plot points or ending of a single work by George Eliot, let alone, say, George Gissing (perhaps my personal favorite Victorian novelist!).