I am dubious about any definition of "puzzle" for which the claim "This puzzle is not fun" is tautologically false, regardless of either the speaker or the puzzle in question.
If a puzzle is not fun, it is a chore, a problem or in the worst case, high school math homework.
People want to tell everything instead of telling the best 15 words. They want to learn everything instead of the best 15 words. In this thread, instead post the best 15-words from a book you've read recently (or anything else). It has to stand on its own. It's not a summary, the whole value needs to be contained in those words.
I'll start in the comments below.
(Voted by the Schelling study group as the best exercise of the meeting.)