What haven't you read, that you should have read?
I guess that shows the limits of my education... and I guess that applies to both parts of the above paragraph.
I'm trying to think what I consider embarrassing not to have read - I guess it depends on what I consider my field to be. I'll have to think about this a bit more and see if I can come up with anything, as my brain is too tired to think about such heady things as this.
And this is a further thought, from the comments:
"Wonderful question, and if you also asked which is the book one is most embarrassed to to have read, boom, you could read a person's character through the answers to those two questions."
And also, this article from Slate, which starts with:
In his novel Changing Places, David Lodge describes a literary parlor game called "Humiliations" in which participants confess, one by one, titles of books they've never read. The genius of the game is that each player gains a point for each fellow player who's read the book—in other words, the more accomplished the reader, the lower his or her score. Lodge's winner is an American professor who, in a rousing display of one-downmanship, finally announces that he's never read Hamlet.
I think I would like to play this game, especially after a couple glasses of wine.