Your question is subjective, of course. It would certainly be possible to ask it of a given person, and that person might answer, "nothing". After all, difficult as it is for me to understand, there ARE those persons who do NOT find the novel interesting!
Also, we might ask the question of 20 persons, and all would have different answers, none totally agreeing with the others. Therefore, I cannot tell you exactly what is interesting about the book. You will have to read it and decide for yourself. However, I can give you a couple of suggestions of what makes it interesting to me. Perhaps these will give you some clues as to how to begin formulating your own answers.
First of all, I find the setting of the book to be quite interesting. The description of the heather, the rocky topography, the wind, etc., always evoke, for me, a land that is far removed from my own, and one that I would like to view.
I also like the Gothic nature of the book. The dark, brooding, questioning, uncertainty, passionate nature of the characters draw me into their personalities. "What makes them tick?"
And, of course, one cannot overlook the fact of the romances between the two main couples. Love and romance for one couple is extremely different from the love and romance of the other. The place of status in society of the era has much to do with their relationships, and makes their actions extremely interesting.
The fact that the novel was written by a woman, during a time when female writers were neither so numerous nor so appreciated as they are today, also gives me another reason to be interested in the book.
These are only some of the reason I find "Wuthering Heights" to be of great interest, and a novel that I have read more than once. I hope this will give you some starting places for your own conclusions.
I will start off with my reason why the novel 'Wuthering Heights' by Emily Bronte is so interesting - hopefully other editors will chime in with some more variations for you. It's interesting because the book broke the mould of its time. In the first half of the 1800s, femininity was everything to the upper classes - in fact girls would fail to have a good match or living without it. Girls were expected to be delicate, gentle, passive, talented in the gentler arts of music, conversation, sewing and to be learning to be good hostesses - in other words to be ladylike accoutrements their rich husbands could be proud of. Emily Bronte was different - not only did she pursue the unladylike occupation of writing for money, but she wrote 'coarse' or 'vulgar' stories involving passion and rage. In other words she was more honest than many writers of her day.
reader sad when he dies.
There is a villain. Hindley is hateful to Heathcliff from the very first time he ahs to deal with him. He resents having to accept him as a brother and that he is expected to be presented in public with Heathcliff. When his father dies, he decides to reduce Heathcliff to a servant. He treats him miserably.
Heathcliff is handsome and moody and dedicated to Cathy. His love is stronger than his won identity. After he believes that she will marry Edgar Linton he leaves. The twst comes because she had actually decided not to marry Edgar because she is a part of Heathcliff. Heathcliff does no stick around to hear this part.
The mystery begins as Heathcliff returns a rich gentleman. He seeks his revenge on Hindley. He seeks his revenge on Edgar. He manipulates Isabelle into marrying him. Still he does not get Catherine back.
Our hearts break for Catherie who is torn between her duty to Edgar who has been so good to her and Heathcliff who is moody but holds her heart. She dies before she can ever have Heathcliff. Heaathcliff blames Edgar on her death and sets out to destroy him.
One can not help but be sympathetic for both men, Heathcliff because he does not get Catherine and Edgar because he does but only in body. Edgar is a poor victim in the situation. Heathcliff is cruel to his son by Edgar's sister.
The novel is about denial and the depth of Heathcliff's love and Cathy's connection to Heathcliff as well as the gothic structure and effects makes it great reading with characters who stay with the reader.