;)PLease discuss the nature of Heathcliff and Catherine relationship ?Why there is extreme Love and extreme Hate in the novel?

I never got what the big deal with this novel was. It wasn't very romantic. And Heathcliffe just took all his pain and suffering and imposed it on others. It would have been more romantic had he not turned so evil. I honestly do not undertsand how it is a classic, it's not near any of Austen's, or Brady's classic novels.