Mystery Fiction is a genre of fiction usually involving a mysterious death or a crime to be solved. Often with a closed circle of suspects, each suspect is usually provided with a credible motive and a reasonable opportunity for committing the crime. The central character will often be a detective who eventually solves the mystery by logical deduction from facts presented to the reader. Sometimes mystery books are nonfictional. "Mystery fiction" can be detective stories in which the emphasis is on the puzzle or suspense element and its logical solution such as a whodunit. Mystery fiction can be contrasted with hardboiled detective stories, which focus on action and gritty realism.
Thriller is a genre of fiction, having numerous, often overlapping subgenres. Thrillers are characterized and defined by the moods they elicit, giving viewers heightened feelings of suspense, excitement, surprise, anticipation and anxiety. Successful examples of thrillers are the films of Alfred Hitchcock.
Thrillers generally keep the audience on the "edge of their seats" as the plot builds towards a climax. The cover-up of important information is a common element. Literary devices such as red herrings, plot twists, and cliffhangers are used extensively. A thriller is usually a villain-driven plot, whereby they present obstacles that the protagonist must overcome.