Race/Class/Education - Throughout the novel characters are prejudged by their race, class or education. When Heathcliff is first introduced he is described as a dark skinned boy with dark hair, and because of this people are prejudiced against him. He is called a 'gypsy' numerous times, and the Lintons treat him badly and send him away from their house because of his appearance. Heathcliff also quickly dislikes his son because of his light skin and hair.
Class is also an issue. There was a class hierarchy in Bronte's England, and this can be seen in the novel as well. The residents of Wuthering Heights seem to be of a lower class than the Lintons at Thrushcross Grange. Even though she loves him, Catherine will not marry Heathcliff after he has been degraded, and instead marries into the rich Linton family, causing all of the major conflict in the novel. The Lintons are of a higher class both because they have more money and don't seem to have to work, and because they are better educated.
Catherine tries to better her station both by marrying Edgar Linton and by her constant reading. She laughs at Hareton because of his lack of education. Heathcliff admits that Hareton is smarter than Linton, yet because of how they are raised and what they will inherit, Linton will be the more upgraded while Hareton will remain a servant. It is only when Catherine and Hareton become friends and she begins to educate him that Hareton turns into a gentleman and loses his crude behavior.
Revenge - Revenge is a major theme of the novel. Early in the novel Heathcliff is described as plotting revenge, and the second half of the novel is dominated by Heathcliff's revenge against Hindley and his descendants for his mistreatment of him and against Edgar and his descendants for Catherine's death. Heathcliff's revenge affects everyone in the novel, and he seems to think that if he can revenge Catherine's death, he can be with her. He has been looking for her since her death, as he has been sensing her near him. However, it is only at the end of the novel, when he has given up his plans for revenge, that he is able to see Catherine and that he is reunited with her.
Supernatural - Supernatural events happen in the very beginning of the novel and continue until the very end. In chapter three Lockwood is grabbed and pleaded to by Catherine's ghost through a window, and in the last chapter Ellen talks about people seeing the ghosts of Heathcliff and Catherine walking on the moors. In between Heathcliff tells Ellen about hearing Catherine sighing in the graveyard and sensing her nearby, and when he gives up his plans of revenge he even seems to sees her ghost. Ellen also once sees Heathcliff as a goblin, and wonders if he is a vampire or a ghoul, although she realizes she is being silly. These themes and instances are tied to a spirituality and life-after-death theme in the novel. Edgar and Heathcliff both want to be with Catherine after she has died. Edgar does not want her to haunt him, but he does look forward to a time when they can be together again. Heathcliff does want Catherine to haunt him, and she indeed seems to, and he also looks forward to spending eternity with her after death.