Yeah, its out of continuity. It’s basically the end of the Superman story, its like John Wayne’s Shootist. DC has many insanely good out-of-continuity stories for Supes and Bats; I find when reading them I just read TPBs of the arcs that I enjoy and ignore their individual continuity altogether. I collect all of the JLA titles and crossover tie-ins, so that is how I keep up with their continuity as far as its relevant to the rest of the DC universe.
The DC Injustice universe is pretty sick. Their DCeased series was also insane.