Batman (anything by Frank Miller - one of his Batman comics was the basis for TDKR with Christian Bale)

I would personally steer clear of The Dark Knight Strikes Again.

I didn't see it mentioned here so I'll chime in with Grant Morrison's run of Animal Man. I'm not usually a superhero guy, but Animal Man was one of the best comic books that I have ever read. He really turns the whole format onto it's head and really dissects medium.