Mystery refers to the incompletion of anything on a topic . It means suspens.Mystery is, not knowing the truth about some event that happened or about a person. We do not anything about the life after death and what happens after. It is a mystery still.  Mystery is absence of any information on a topic or about a person of interest to us or to the society.

Further on...

    People like mysteries. It thrills them.  The suspense in a mystery thriller story holds the persons attention strongly, holds the heart beat, all the concentration and focus of the persons.  It is just basically in the human nature itself.  We just feel intrigued by suspense and we cannot tolerate it in the nerves for a long time.   Some people even could face heart-attacks due to the stress on the nervous system.  After a mystery is unravelled, we feel so relieved in the nerves and happy in the mind.

   Many serials on TV, magazines, thriller books, and cinemas do well because of the tense excitement that they create during some moments.   They cash in on the weak points of the audience.  Usually darkness, ghosts, haunted houses previous births, aliens from spaces, and other topics form the story lines of the mystery thrillers.

   The persons who solve mysteries are very accomplished, respected and fantasied.  Often people are crazy after the heroes.  Mysteries are everyday lives for the police force and detectives. 

Example :-

We don't know much about the black hole. A black hole is a place in space where gravity pulls so much that even light can not get out. We can't get any reason for it .

Conclusions :-
Peoples are very fond of thrills and spice so they like mystery stories / films/fiction very much .We need to be systematic, logical, knowledgeable, wise and energetic to be heroes of solving mysteries.  Let us solve the mysteries that lie ahead of us.
we are all familiar with mysterious happenings-happenings which cannot be rationally logic has been able to solve such happenings.such happenings include the mysterious disappearance of ships and planes in Bermuda triangle,the disappearance of dinosaurs,the appearance of of the U.F.Os etc.this section includes various theories,myths and strange happenings. 
example:harry potter:
In 'harry potter and the philosophers stone',a mystery novel by J.K Rowling,we find ourselves in a strange world.the mystery about the wizard who killed harry potters parents continues to grapple us a Hagrid is reluctant to name the murderer.