It's based on a Frank Miller graphic novel from 1986. Available in .PDF format at your favorite "store".This actually piques my interest. Any link to all the reading materials based around this?
This the one where
Spoilerthe Joker breaks his own neck in that amusement park?
How can Batman take a punch from Superman?
Even fully powered, Superman always pulls his punches vs. mortals. But (in the story,) after a recent run in with an atomic bomb, Superman's power levels were severely reduced which explains his susceptibility to Batman's attacks.
ah I see this is one of the stories where superman decides to pretend he's not basically a god. probably takes place in his timeline right after he he turned back time and right before he destroys an entire planet.