It doesn’t always take much to get a reader to root for a character. You can start a story with a guy running, and as long as he’s just enough of an underdog (being chased by something ferocious, or multiple people, perhaps), the reader immediately wants him to make it out alive. But once he does make it out alive, he’s going to need to win your reader over or they’ll happily set down the book.
Of course, not every story has the advantage of action-packed, adrenaline filled leverage. Sometimes none of the characters are in physical danger, and all that’s at stake are friendships.
Or, if you really fucked it up, toward the end of your book when your main character is fighting the villain for his life, your reader realizes they don’t actually care who comes out on top.
In these more subtle examples, it’s important you create a character interesting and likable enough for the reader to care.
Characters are almost everything.
What would The Catcher in the Rye be without Holden Caulfield? Love him or hate him, he is the novel. What is Gone with the Wind without Scarlett O’hara? Fight Club without Brad Pitt –er, I mean Tyler Durden?
Even in stories where the setting carries the day, there still must be characters to do shit. Middle Earth is fine and good, but I find it much more enjoyable to follow an antisocial hobbit around rather than admire the scenery as though looking at a photograph.
So, what makes a good character?
That means the character has interests, a backstory (whether or not it’s told), likes and dislikes, flaws, ambitions or lack thereof. They have a personality.
Your character has something they want or need. That’s the driving factor behind them, right? The goal can be simple, especially at first. Maybe your ornery ogre just wants all the fairytale creatures out of his swamp in the beginning.
People can’t relate to perfect characters. Flaws don’t make your character unlikable, though ideally they should make them less likable. Maybe your character is abusive toward someone else but upon realizing it attempts to reform. That doesn’t happen overnight; that’s a story. Maybe they involuntarily grimace when they look at children. Maybe they enjoy pop country music. The world is your jacked up oyster.
For every several flaws, there should be some tiny redeeming quality (if you’re going for the only semi-likable type, anyway). Maybe she’s a douche to everyone she meets, but she takes her cranky ass to the soup kitchen to volunteer every weekend. Or he calls his grandma every night. Or they’re kinda nice to the kid everyone bullies at school.
Characters need more than good looks and being kind to be beloved to the reader. And in stories that aren’t action/setting heavy, they can make or break the success of your writing.