In general I probably would but there are these certain kind of stories which are meant to shock people or surprise them. And having a warning would ruin it. But yes, in general I would like a warning myself, I'm just saying there are incidents where it wouldn't fit.

I recently read a book which was a rather ordinary story about adultery. Until in the middle of the book it is suddenly revealed that the person telling the story is a woman not a man. And all the hot sex scenes you just read were lesbian. Now I guess in Bush's America that book would not have been sold without a warning. But in doing so it would have ruined the book completely.

Not the same but again the element of surprise.