Catherine is a fan of novels, specifically Gothic novels. She is pretty but not beautiful, smart but not brilliant, good-tempered but prone to flights of fancy. In essence, she is an average girl. Her experience in society is limited, as is obvious in her alternating outbursts and missteps in dealing with both the Thorpes and Tilneys. Her guiding character tends to be that she believes the best of people—except with regard to the influence of her beloved book, The Mysteries of Udolpho. Under the influence of that novel and others of its kind, she suspects General Tilney of murder.
Henry—the hero of Catherine's story—is witty, smart, and attractive. He is not the heir to his family's estate. His primary traits are those of both kindness and patience. Even as Catherine veers into heightened emotions, be it with regard to doubting Frederick or trusting the Thorpes, Henry steadfastly asks guiding questions until she comes to rational conclusions. Ultimately, he stands up to his father on Catherine's behalf and waits until the general relents and approves his request to marry Catherine. He is a man of morals and patience.
Isabella is conniving. Her goal—to obtain a successful and wealthy husband to improve her social status—motivates her machinations. Considering the acceptability of such actions at the time, she is not unusual in this. Isabella immediately befriends Catherine, misunderstanding Catherine's social and economic status. Her actions throughout the entire novel are self-serving and at odds with her words.
John is arrogant, assertive, and unappealing to Catherine. Even though he courts her, Catherine is apparently oblivious to John's advances. Her obliviousness is confirmed when Isabella reveals her brother has written to her about Catherine, who is shocked by this revelation. It is John's ongoing deceit and lies that lead to Catherine's expulsion from Northanger Abbey. He initially lies to the general about her wealth, and then after she has rejected his proposal, John lies again to accuse Catherine of social climbing. His primary traits are deceit and arrogance.