The emphasis on the natural world, the presence of the supernatural, the overarching idea of an indestructible human spirit and the general emotional angst of the characters renders Wuthering Heights a sort of cross between Romantic fiction and Gothic; it is probably for this reason that its early critics and readers alike were annoyed and confused.  It was not at all similar to what was typically being published in Victorian England at that time, probably another reason for the outpouring of negative responses it initially elicited.  Today, however, it is generally seen as a masterpiece of literature, partially because literary critics and scholars still cannot agree on whether it is a truly Gothic or truly Romantic work.  Bronte's refusal to force her novel into one tradition or another is consistent with her characters, who she treated with the utmost complexity; none of them are completely good or evil, sympathetic or unsympathetic--another characteristic that probably baffled readers, as Victorian literature typically operated on structured guidelines regarding characterization.  A sympathetic character who was also flawed didn't typically fit into a Victorian literary piece, making Bronte's characters all the more unique, interesting, and provocative.