Final answer:
The mood in the novel 1984 is gloomy and depressing, reflecting the dystopian society depicted by George Orwell. The warning in the novel is about the dangers of surrendering critical thinking to a centralized government.
Step-by-step explanation:
The mood expressed in the novel 1984 can be described as gloomy, depressing, and dystopian. George Orwell portrays a society under a centralized government that controls every aspect of life, resulting in a loss of individual freedom and critical thinking. The warning in the novel is that if people surrender their ability to think critically and question authority, they risk living in a totalitarian state where their thoughts and actions are monitored and controlled.