The Top 10 “Top 10″ books: The editor asked 125 authors to list their Top 10 books of all time.
Some people might think that the lists will be mostly the same, containing among them (say) thirty or forty books, but experience (see The Long Tail) tells us that the lists will be different — a lot.
Indeed, the 125 lists contain 544 books among them.
So each book appears in an average of 4.352 lists out of 125. (Of course not.) (Exercise: What is the expected number of books that two random lists (out of these 125) have in common?)
There are 23 that appear as the greatest work of all time on one author’s list, but are not even present in any of the other 124 lists.
The sad fact is that I have read too few of them.
[Answer to exercise: I'm an idiot, can prove that neither question can be answered without further data.]