What a joke. I am sure and vaguely remember being assigned that book back in the 70s but did I read it? No, not completely. NO ONE READ TO KILL A MOCKINGBIRD VOLUNTARILY, NOR ENJOYED IT. A favorite novel?! What planet are they on?! Okay, talking about planets, I read science fiction, how about we talk about Heinlein, Anderson, Asimov, Niven, Silverberg, Norton, Haldeman, and so many others?
I think that's actually true. For the last fifty years or so, anyway.
But many people have only read the novels they were assigned to read, and they don't have happy memories of what teachers made them read.
I guess people also read popular novels down through the years, but whoever is doing the survey isn't going to ask about Stephen King or Judith Krantz or Jackie Collins.
Gatsby and Of Mice and Men end unhappily. Nobody read The Scarlet Letter all the way through. Huckleberry Finn has the race thing. And if you say Catcher in the Rye people will think you are a potential assassin. So what's left?