You might want to consider the classic Gothic technique of narration. We have framing narratives and multiple layers of narrative. At some points, we have Lockwood telling us what was told to him by Nelly Dean what was told to her by another character. Such levels of narration create deep uncertainty and force us to ask hard questions about the narrative's reliability.
Bronte uses parallelism to a great degree in the novel. Think of things that come in pairs that play off of one another. There is Cathy and her daughter Cathy. There are two viable men in love with Catherine, Heathcliff and Edgar, but they couldn't be more different in nature. There are two relationships for Heathcliff: the unrequited love of Catherine and the marriage of revenge with Isabella. There is the "adoption" of Heathcliff by the Earnshaw's and the "adoption" of Hareton by Heathcliff. This list could go on -- it is interesting to ask yourself how these parallels enhance the novel as a whole.
Wuthering Heightsis a great example of a Gothic novel. The author uses Gothic elements such as weather, dark atmosphere, supernatural allusions and melodrama. The dark and stormy night motif is still popular and still effective today, and fans of Twilight owe much to the Bronte sisters!
Perhaps because fantasy was a relief from the bleakness of life and the rigors of religion for the Bronte children, Emily Bronte's Wuthering Heights became a mystic novel of preternatural imagery and characterization brought together in a spiritual triangle which formsthe completion of the conflicts among the members of both the Earnshaw and Heathcliff families. Along with this completion of conflicts is the resolution of the problem of alienated, lonely orphaned individuals who populate the narrative.
When Mr. Lockwood first arrives at the Heights and must spend the night, he finds on the window ledge of his room a name "repeated in all kinds of characters, large and small," a phrase that is prophetic of the repetition of Catherine Earnshaw's spiritual rebirth in her daughter Cartherine Linton who marries Linton Heathcliff and later Hindley Earnshaw, bringing Catherine's name to the original one of her mother, thereby completing the spiritual triangle as there is the resolution of the orphaned condition of the children as well as the return to the point of origin. Catherine the first is spiritually reborn as a soul that is less turbulent than that of her former self.
In addition to the spiritual triangle, there is imagery of nature that is preternatural. The wild, melancholy, and tumultuously beautiful Yorkshire moors lend a mysticism to the setting in which Catherine and Heathcliff's is elevated at times to the sublime. The moors serve as a supernatural region that has no boundaries in contrast to the house and other areas. In fact, in numerous places in the novel the two houses, Thrushcross Grange and Wuthering Heights are referred to as prisons. Like the setting, Heathcliff's and Catherine's "mutual joy" with one another surpasses what seems human; it is, indeed, a metaphysical passion. As she speaks with Nellie, Catherine tells Nellie of Heathcliff, "He's more myself than I am....Nelly I am Heathcliff." Even after her death, Catherine's ghost inhabits the heart of Heathcliff, a ghost generated from the haunting presence of the mysterious moors.