I may sound like a jerk, but I am typically surprised when I come upon a word I don't know, especially in a mass market publication, since I have a high opinion of the quality of my own vocabulary.
But today, while reading Vanity Fair, I came upon not one, but two words I didn't know.
The first was, "He cast a gimlet eye..."
Now I know what a gimlet is, and love to drink one from time to time, but I have no idea what a gimlet eye is. According to dictionary.com, gimlet as an adjective means: able to penetrate or bore through. Never heard of it. But it's based on the definition of gimlet as a noun: a small tool for boring holes, consisting of a shaft with a pointed screw at one end and a handle perpendicular to the shaft at the other.
The second was a description of a man as insuperable. The bad part is that the sentence gave absolutely zero clue as to what the word meant, but here it is: incapable of being passed over, overcome, or surmounted: an insuperable barrier. Again, never heard of it.