My theory, emerging during this 50 in 2014 project, is: Great literature both motivates you to read and makes you think for a long time afterwards.
I used to think great books had to be enjoyable. But this one is great and wasn't.
It was painful.
Painful because these people's lives were.
Painful because you know the ending before you start.
Painful because there's beauty alongside suffering.
Like life.