What's the Difference Between Cuthartic and Sham?

As a reader, i tend to be am. And i chastise myself for this because it makes me really uncomplicated. But i tend to being the kind of reader who like, roots for everything to work out. I wanted bad things to keep happening to the characters that i liked so that the book would keep going rigt. It made me wonder how much a book's ability to let a reader privately explore their worst impulses or most shameful sides as a human being is also maybe what makes us so fond of that book.