Mood includes many literary choices that an author may choose to make. For example, the words an author chooses to use can create a mood. In addition, whether a piece is written from the first person point of view or in another way also affects the mood. For example, if an author tells a story in the first person point-of-view, it seems personal or confessional. If an author chooses third person narrative, the mood conveyed would be more objective. In addition, if the dialogue is between two characters who are fighting then the mood would be tense or argumentative.
The other literary device is suspense.Suspense is created by withholding something--whether it be critical plot turns and twists or information about a character's motives or actions done by a character that nobody knows about until the end of the novel. Suspense is essential to mystery because the author does not want the reader to understand the mystery until the end. Suspense is not only developed in murder mysteries. It is created in many stories and novels by alluding to something that happened, or is going to happen in the future, but not saying what that is until the end.
Mood and suspense go together. It is all up to the author whether he or she wants to create a certain mood in their novel. I don't think an author says to herself, I am going to create the mood of sadness then makes a scene. I think the author says to herself that she wants to create a certain character then that character faces difficulties in life. Then how they react to those troubles causes a mood in the scene. However, I do think it is a conscious choice to use suspense. Suspense keeps the reader turning the pages. It picques the readers interest. It is beguiling. Suspense is essential for good literature.