Wuthering Heights is a Gothic novel with an undertone of romance. Gothic novels became extremely popular in England, from the 18th century through the Victorian era when Brontë wrote. Supernatural elements are the genre's most famous characteristic, and Brontë fulfills that convention through the appearance of Catherine's ghost (or at least the teasing possibility thereof) in Chapter 3; Brontë leaves it ambiguous whether the ghost was literally present or just a dream, but strongly hints that Catherine's spirit truly does haunt the Heights. The supernatural is also reflected in the novel's spooky setting: the remote, windswept moor and 300-year-old Wuthering Heights with its gargoyles, stunted trees, and air of neglected grandeur. Old, historic, crumbling buildings are a major feature of Gothic literature, helping create a tone of dark, mysterious history, isolation, and potential danger.
By Brontë's time, the genre also had a growing association with the human subconscious and repressed desires, which is clearly explored in Catherine and Heathcliff's relationship and its dark effects. Relatedly, Gothic novels also frequently contain a revenge element—clearly seen in Heathcliff's heartless plotting across decades and generations—and plots involving imprisonment, as when Cathy and Nelly are detained at Wuthering Heights to force Cathy to marry Linton.
The use of melodramatic language—especially Catherine and Heathcliff's frequent use of heaven and hell as metaphors for romantic bliss or romantic torment, as well as Heathcliff's tendency to express the desire to brutally murder those he hates—is another marker of the genre. At the same time, Lockwood's sometimes wry, sometimes horrified, and almost voyeuristically fascinated tone as an outsider fits the genre while also, perhaps, poking subtle fun at its excesses.