For me it was Sandman.
Neil Gaiman announced that not only was he doing a super-hero book, but that the book was being done for Marvel, not DC. It caught me off guard, and piqued my interest. At that point in time I knew Neil could write, but I didn't see him as a writer who belonged in the super-hero genre. Here was a man who had fashioned a deep, dark and sometimes disturbing mythology that entwined Christianity with Norse, Pagan and other religious beliefs announcing that he was going to do a story that included Captain America, Nick Fury, Spider-Man (BLAH!), the X-Men and more.
It didn't make sense.
I can admit that the introduction to that graphic novel, written by Peter Sanderson (a cultural critic and historian who specializes in comics) is what opened my eyes to the bigger picture that was being painted within the book. First of all, as a person who enjoys history, it's embarrassing to admit that somehow I lost sight of the fact that Gaiman had found the perfect era in which to set his tale. Europe was teetering on the brink, with all manner of political and religious forces push and pulling it towards what must have looked like a recipe for Armageddon in those years. He then uses all of these forces as ways to craft a new Marvel mythology.
And there's the piece I always missed.
Having reread this story with fresh eyes, I developed a new appreciation for its richness and scope, its historical narrative and its observation of the dangers of dogma. Are there still things I don't love about the book? Of course there are. Steve Rogers, knowing his presence in 1602 threatens the existence of everything, does not agree to return from whence he came? Sorry, but that's just not Steve Rogers. But that is perhaps my biggest complaint these days, and it is handled with the guile and cunning that only Nick Fury can bring to a situation.
In the end, if you have read this tale before, or never read this tale, I recommend you take the time this summer to put your feet up on the back deck, maybe get a nice summer ale open for sipping (ice cold wheat ale is suggested) and enjoy a wonderful work of redefined mythology entwined with history.
I'm nominating this one for the Best Story Ever discussion.