MARVEL COMICS INDEX #4
On that same first comic shop trip to HEROES WORLD, I discovered and purchased the Fantastic Four volume of the George Olshevsky MARVEL COMICS INDEX. These handsome tomes reproduced the covers to every issue of a given series, and indexed their contents as well.
I spend literally hours poring over these volumes, wondering about the contents of the various covers they showed, and absorbing every last drop of information contained therein. Much of my vaunted knowledge of Marvel history comes from studying these books–in a way I did no school textbook.
Later editions have covered more issues, and given more in-depth coverage. But these Indexes are still what I turn to first when I need to look up some arcane bit of Marvel lore