There are stories where everyone is basically good, and they’re pretty boring. Then there are stories where some characters are good and some are evil, but those tend to be a bit flat and unsatisfying. Theoretically, the next step up in complexity should probably be shades of gray, but it isn’t. There’s a large body of literature that deals with good and evil by moving characters back and forth between the two. In general, there’s a good character who sometimes behaves badly, usually by having a bad temper, and there’s a character who seems pretty normal at first, but inexplicably turns evil. This character works against the protagonist for most of the book, but is reformed at the end, often on their deathbed.
I’m not describing any particular book here, or even a particular author. This is a pattern that applies to a large chunk of the ordinary novels written between the mid 19th century and World War II. There was a whole body of writers–not the great ones, but ordinary writers–people whose works will never be part of the canon, but who knew how to write, and to create stories people would enjoy, and who earned a living at it. And for the most part, these writers were struggling to make their characters more real. They tried to add complexity in different ways, and while none of their characters seem as if they could jump off the page, most of them work. They’re flawed as people and they’re flawed as characters, and they’re a big part of why I enjoy this kind of book so much.
I tend to fall in love with the suitors the heroine rejects. I preferred Hindley Earnshaw to Heathcliff when I read Wuthering Heights. I once spent a couple of hours arguing with a friend over King Lear because I like Albany better than Cordelia. Characters in forgotten, mediocre novels often speak to me more than important characters in important books.
And when they don’t, they appeal to my sense of the ridiculous.