I'm not surprised. Wuthering Heights is a very difficult book. Told through not just one but two framing devices -- Mr. Lockwood, the tenant, and Nelly, the housekeeper, both unreliable narrators. The servant Joseph's quotes, written in arcane dialect. The unexplored mystery surrounding Heathcliff's origins. The second half of the book, about the offspring spawned by the couples who married in the first half ... and so on.
I first read it in 5th grade and loved it. Read it about 12 more times -- it was right up there with Gone With the Wind and The Godfather (I know, kind of an odd mix).
But as I told my son the other night, I don't think I could get through it now. I don't have nearly as much
patience. And I've never read any other book by a Bront?, not even Jane Eyre.