It may not fit the definition of a puzzle for many people, but the central mystery of Agatha Christie’s Murder on the Orient Express is one of the finest puzzles constructed—and this particular mystery is perhaps why Dame Christie is considered by many to be the finest mystery writer of all time.
A murder occurs on a train, but the train is stopped by a snowdrift. When the murder is discovered, the detective knows that there are twelve people (besides him) in the coach, and he must figure out who the killer is before the train continues on.
It’s a logic puzzle, and the reader is presented with the same clues that the detective sees.
Of course, the book has been made into a movie (several times, actually). As it’s arguably Christie’s most famous book, and the movies were seen by millions, many people know the answer to this puzzle. Upon repeated readings/viewings, the answer may seem obvious, but it was assuredly not so when most people are exposed to this puzzle for the first time.
One requirement I have for a great puzzle is this: an average person should be able to figure it out without an advanced degree or specialized knowledge. This mystery fits that requirement perfectly. It’s the subversion of reader (or viewer) expectations that makes this puzzle so deceptive—and the solution so satisfying.