Often an author's writing emanates from a single poignant question that triggers creativity, and expands to sustain an entire novel. If properly phrased, the question identifies the genre, provides a unique theme, and becomes the novel's big bang that radiates in all direction to form a compelling plot.
Examples:
What happens if bodies begin falling from the sky on concrete highways at night?
Genre: Mystery
Resulting Book: The Protagonist must discover the cause, connection, and the culprit.
What if a man appears whose mind-link with advanced aliens begins solving the world's problems?
Genre: Science Fiction
Resulting Book: A book describing social upheaval as the Protagonist usurps government power while conquering, crime, poverty, war, and disease on planet Earth.
What if England's King George succeeds in suppressing the American Revolution and maintains control of the colonies?
Genre: Historical
Reulting Book: A book describing subversive activities of revolutionaries throughout the colonies that gradually destroys England's economy and support for dominance in America.
What if a brilliant but emotionally flawed engineer wins a lottery and succumbs to a voluptuous but deceitful woman?
Genre: Thriller
Resulting Book: A book describing the Antagonist's deep emotional scars and the desire for retribution.