In fashion not dissimilar to Leone's masterful deconstruction and exploration of the mythological Western, the pairing of Moore's words with Curt Swan's immortal and character-defining pencils is magic: a deconstruction of the hallowed and iconic by a mind matched by few wrapped in a rousing action story with deep emotional stakes; a distillation of, at that point, nearly 50 years of monthly storytelling that not only showed why Superman has endured, but why he must: it's the first work anyone tasked with carrying on that legacy – be it in comics or in film or in any other media – should read; I can only hope that Gunn uses this as a guide – fortunately, from what he's said of what's coming in LEGACY, it sounds like he has. Certainly nailed the casting so far.
Other than Morrison and Quitely's ALL-STAR SUPERMAN (now my second-favorite Superman story and apparently one of Gunn's guiding texts), I can't think of another take that so deeply captures every facet of the character – the hope, the action, the sacrifice, the tragedy – in such a powerful, poignant, and emotionally satisfying way. Essential.