<p>Mark, these comic books are really rare, but these are available as scans in some sites. The chronology in DC Comics is changing since
Crisis on Infinite Earths; from there existed various Crisis, each one changing Superman' history in bigger or lesser degree. To begin, I recommend
Superman: A Celebration of 75 Years (Collected), the Man of Steel miniseries by John Byrne (1986), and all Superman stories written by Byrne. Then, something light, as
Panic in the Sky saga. Then the
Death of Superman and
Return of Superman. About Pre-Crisis stuff, I recommend any story written by
Jerry Siegel (after all he was Superman creator with Joe Shuster),
DC Comics Presents,
Superman Vol 1 400, Sand Superman Saga written by
Denny O'Neil (
Superman Vol 1 233 to 242), stories written by Alan Moore (
Superman Annual Vol 1 11,
Superman Vol 1 423,
Action Comics #583). I DON'T RECOMMEND any Electric Superman story (really), and Silver Age stuff only if it has the first appearance of some famous character or concept.
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