Have you ever read a book where you disliked the main character? That's how I felt when I began reading BEFORE I FALL by Lauren Oliver. Samantha Kingston was a horrible person, and I didn't care if she lived or died. 
Lauren Oliver wrote an amazing story with an unforgettable character arc. By the end of the book, I did care whether or not Samantha survived. As she lived her own Groundhog Day experience, I found myself wishing for a happy ending for Samantha. This was an excellent book, and if you haven't read it yet, I highly recommend it.
In Plot & Structure, James Scott Bell states, "What makes a plot truly memorable is not all of the action, but what the action does to the character. We respond to the character who changes, who endures the crucible of the story only to emerge a different person at the end."
Love 'em or hate 'em, when we're passionate about a character it means the writer did a great job of developing a pretend person that feels real and stirs up strong emotions.
Do you remember a character you didn't like, but who won your heart by the final chapter?
photo credits: Barnes & Noble