It can be difficult for the readers to follow a series, when back-stories of characters suddenly change, and certain events and interactions can no longer be taken at face value. Things get messy if you read two stories, and there isn’t a clear path to show how characters got from Point A to Point B.This problem is further complicated by the differences in the ways individual fans will select stories stories to read. Some will stick exclusively to new material. Some will read mostly reprints, although the order in which older stories are read may differ. And plenty will read both new material and reprints. There are more formats for all this stuff than ever before, with hundreds of Spider-Man TPBs, thousands of back issues and a lot of material available on Marvel’s website for a $2 iPad download, or a $60 annual subscription.
The changes in back-stories are confusing enough with new revelations, such as the discovery that Ned Leeds wasn’t the Hobgoblin or that the Falcon was actually a pawn of the Red Skull’s when he met Captain America. In those cases, things still happened as it literally appeared on the page. There was simply a new context, based on things that happened off-panel. A reader who skipped the title for a few months may briefly be confused, but there is at least a clear explanation.
One More Day represented a different type of retcon, so that in some cases, what you see on the page had to be reinterpreted as if it had occurred in a different universe. For some readers, this was just a bridge too far, though I would argue that most readers have proven themselves capable of this type of mental gymnastics.
Technically, the entire Marvel Universe is consistently retconned, with every new reference to contemporary events and individuals. The Peter Parker of the Lee/ Ditko run did not grow up in the 1990s. That retcon is necessitated by having Spider-Man be a guy in his mid-twenties in comics published in 2012.
Filmgoers have to deal with this kind of stuff all the time, recognizing that a character who appears in front of the camera is not actually the guy who hosted Saturday Night Live, or starred in that other movie, even if this is all going on in your mind during the performance. If a film is based on a true story, you may later learn how the filmmakers embellished things, and make allowances for that, creating an image in your head of what really happened.
An interesting retcon occurred in Ed Brubaker’s Captain America. Right before Bucky returned, it was revealed that most World War 2 era Captain America & Bucky stories were sanitized versions of their actual adventures, in order to obscure Bucky’s true role of doing the dirty work Captain America couldn’t for PR reasons. That was a lot cooler than the previous take on Captain America’s sidekick, the one character Stan Lee didn’t know what to do with.
Many readers had seen at least a handful of the Golden Age Captain America stories, as those had been reprinted a few times. And those stories informed the take on Captain America in later years. Bucky wasn’t exactly slitting throats in the Lee/ Kirby flashbacks (reprinted in the Essential volumes, and the basis for much of the recent movie) or in later World War 2 era Captain America projects.
The explicit revelation that the pre-Brubaker World War Two era Captain America stories didn’t happen the way you read it was worth it, but it does require slight mental aerobics, on par with imagining Mary Jane as Peter’s live-in girlfriend rather than his wife in certain back issues.
I don’t take very seriously the complaint that the multiple timelines make Amazing Spider-Man prohibitively confusing. The books rarely reference the “real” timeline in which Peter and MJ were married, but this should be readily explainable to anyone who could understand It’s a Wonderful Life, Back to the Future (maybe that’s why Bob Gale was on the book) or the right episodes of Family Guy and Futurama, which have all dealt with similar plots. Hell, Spidey had an erased timeline in House of M.
Some fans have a tendency to overthink things, expecting radical changes when none are required. You’d have some questions with easy answers. Would Kraven’s Last Hunt or the early encounters with Venom have gone any differently? Would Spider‑Man have given up the black suit if MJ was just his girlfriend when she asked him to do so? If people no longer remember that Peter Parker is Spider-Man, what happened in stories which hinged on others knowing the secret such as “The Kid Who Collects Spider‑Man,” “The Night Gwen Stacy Died,” and any Venom or Harry Osborn Green Goblin story? The answers in order: No. Yes. Nothing Changed.
There was no suggestion in Quesada’s stories that the amnesia spell was retroactive, changing the world so that no one ever learned that Peter Parker was Spider-Man. They knew and they forgot. If Peter & MJ were in a committed relationship instead of being married, there was no reason for MJ to be less worried when Peter went missing and Kraven started dressing like Spider-Man. Or for Peter to be less understanding when she said that the black costume freaked her out, after the encounter with Venom.
Some would argue that all the writers had to do was clearly establish the status of the characters in the Brand New Day books. Revealing how the current status quo was reached is unnecessary. All the readers need to know to understand the new books is whether Venom hates Spider‑Man—easy to establish—or whether Kraven or Harry are dead, and that’s only when that’s relevant for a storyline in which those characters appear. How long it took Spider‑Man to stop wearing the black costume isn’t much of an issue for the average Spider‑Man VS Vulture arc.
With his retcon, Joe Quesada decided to go further than the bare minimum, providing an explanation that allowed the backstory to remain mostly intact. He didn’t even alter the one thing Dan Slott would have liked to change.
What Would Spidey Do? 
Just curious, what was the one thing Dan Slott would have liked to have changed?
Love your entries as much as I love the character!
Nvm, saw what it was in the next post!