Good mysteries are fun because they keep the reader guessing. One of the most important keys of writing a mystery is writing the story so the reader can try to solve it. Nothing’s more annoying than not being given clues to solve the mystery unless those clues are so obvious that there is no real mystery to be solved. The best way to achieve both goals is to give quality clues but constantly keep the reader guessing so they don’t recognize the clues for what they are.