This issue is a variant of Superman (DC, 2006 series) #651 [Direct Edition]. There exist further variants.
A "1 Year Later" tie-in.
Alternate cover for second printing, pencils only with red shadings instead of full color for the title and the Superman logo.
Story continued from Action Comics (1938 series) #837 and continues in Action Comics (1938 series) #838. The table that Metallo is laid out on is an homage to the kids game "Operation".