All-Star Superman #12 is a fascinating contrast to "Batman RIP" and Final Crisis, the two other Morrison series going on, because both of those stories totally lost their footing last issue and even at their best, you came out of them thinking, "I appreciate what he's doing" while All-Star Superman bypasses intellectualizing and just feels perfect.
As expected, everything sort of comes together in the final issue of All-Star Superman, but it's not in a back-story/continuity obsessed way nor is it a kind of stand-alone, super satisfying way either. The whole issue's like the rest of the series--and like the best Morrison writing--a wobbly, non-narrative, but forward moving nonetheless, trip through lots of ideas both heady and silly, with the right amount of sincerity and emotion, and a scene or two that totally understands the mythology and iconography that make comics goofy kids stuff and the shit that makes grown-ass men like myself tear-up.
The opening scene, a dream-but-not-dream sequence between Superman and his father, ends with Superman getting a choice between occupying the place "individual awareness builds for itself", either heaven ("thought-palaces") or hell, or "to turn and face down evil one last time." The Morrison-ian touch there is that we decide upon death, whether to occupy heaven or hell, and that returning to Earth to live a little while longer, isn't any kind or relief or pardon, but Superman takes it anyway because he's that dude.
The entire series has been about death and Superman dying but it's been a given since issue one, sucking out the silly "we're killing a hero" crap companies do to get more readers and just sort of moving ever closer to that inevitability. The fact that it was announced in issue #1 and that it was known the series had twelve issues, made the death of Superman a reality, but a reality like the weird/sad understanding that your parents or pet will die. You know it's coming and you have some sense of when, but it's still pretty heavy.
It's Morrison bringing palpable mortality to comic books. He did the same thing in issue #1 of Final Crisis when he killed-off Martian Manhunter like it was nothing, joked about it ("let's pray for a resurrection" said Superman), and totally didn't dwell on it all; it was like a real death, quick and unexpected and meaningless. Here, it's less cynical--I assume because Morrison cares a little more about this series--but the effect is the same.
Quitely's art too, seems concerned with the flesh, as Superman and Luthor look particularly lumpy in this issue. He's been slowly making them skinnier and the entire look of the series, while still relatively bright and rotund, is getting more lines and wrinkles but here, it's almost too much. Too much in the sense that this final issue isn't as fun to look at, but that's a good thing.
It's telling that some of the most well-wrought imagery, that which doesn't have this almost Leinil Yu-esque line scratchiness to it, is of destruction--a crumbling Krypton space-station, debris on the floor of the Daily Planet, and the brilliant page where Lex is struck by a car--which makes sense in a comic that ultimately, finds significance and beauty in things coming apart and not working out perfectly. Superman defeats Luthor, but you almost feel fucked up about it. Luthor's no longer any kind of threat and he pathetically doesn't realize it, and Quitely illustrates each glob of blood that flies off his face from Superman's punches as ugly as possible. Even the final Superman/Lois embrace is a little off because Superman's not wearing his cape, Superman's cells are slowly deteriorating, and Lois is crying (the tears too are ugly, like Luthor's blood). Of course, this all makes it more affecting.