The Krypton Companion, edited by Michael Eury (TwoMorrows, 2006). You used to be able to find this sort of inspired and maniacally detailed fan archeology only in the pages of mimeographed fanzines, only obtainable if you were personally connected somehow to their creators. As progress, wealth, and aging fans coming into their own continue to spread their multitudinous benefits, we now have entire beautifully designed and copiously illustrated books celebrating our love and memories for the Man of Steel's post-Golden Age, pre-modern (John Byrne reboot) years.
To be sure, if you have no idea what the words "John Byrne reboot" signify than this book is not for you. And yes, this sort of fanatical fan takeover of the world of and market for comic books that this book exemplified has been in many ways detrimental to the market health of the industry as a whole (though, after a pretty horrendous '90s, I think a lot of the standard DC/Marvel superhero fare is looking much better nowadays).
But as an old fan nostagiac himself (though not about this particular material–I don't think I'd read more than 10 issues of the 1958-1986 era Superman covered here until a few years ago myself, though the Mort Weisinger-era mania had always been a fascinating legend to me, largely through the amused and appreciative cartoon criticism and history of Fred Hembeck) I got more kicks out of this book of interviews with and essays about the writers, artists, and editors who made Superman what he was/is than out of any given 30 issues of an actual Superman comic, any 3 episodes of Smallville, or an infinite number of Superman Returns.
Historians of American culture owe Eury and his indefatigible publisher TwoMorrows (whose Alter Ego zine I've previously praised) a debt of gratitude for their relentless interviewing and documenting a part of American cultural life that's still an engine of enormous wealth-creation for our proud American megaconglomerates (if not for the comic creators who made him), and still a modern myth of great entertainment value in all its glory and absurdity, all its workmanlike repetition and fershlugginer imagination, all its Lois Lanes and Kryptos and Legion of Superheroes.