I've read a lot of middling things about this mini-series. I gave Batman Damned a try, and it was okay. So, I'm gonna give the Black Label Superman a try (probably this weekend).
Elseworlds Superman stuff is some of the best that there is. If you haven't read Kingdom Come, I'd recommend that. It's a Justice League mini-series, but I would say Superman-centric.
Never read All-Star Superman? Some would say that it's his definitive series. Just a couple of titles to think about if you'd like to read more of him.