I think I may have a penchant for dark and depressing stories. I have heard many people say that they disliked Frankenstein and Wuthering Heights because they are creepy and depressing. I loved both of these books! I got so much out of reading them. They gave me much food for thought for days after I read them. This is, to my way of thinking, a sign of a great book. If it can get you to think long after you have put the book back on the shelf then the author has done its job.
In Wuthering Heights, I have to agree that the darkness was a bit too much in parts. The way Heathcliff treated his son and Cathy was disheartening, to say the least. But there were a few things that this book said to me. 1) No person can derail the human spirit-- Heathcliff treated Cathy and Hareton abominably but after he was dead, they were able to attempt to have a 'normal' life. When Lockwood comes upon them at the end of the story, the two are teasing each other somewhat lightheartedly. This says a great deal about the perseverence of the human spirit.
2) If there is no repentance for a life of sin then that life is lived in torment. Heathcliff had many opportunities to make things right and repent but he chose to keep on his dastardly path. As a result, he lived a tormented life even up to the end.
I am sure there are many more things to say about this book but the above 2 were the things that jumped out at me. Now I need to find another dark book to sink my teeth into.