Marvel promises a Spider-Man moment as shocking as the death of Gwen Stacy this May

gamesradar.com:

The first year of writer Zeb Wells and main series artist John Romita, Jr.'s run on Amazing Spider-Man is coming to its close with a story Marvel Comics is billing as "the most shocking issue of Amazing Spider-Man in 50 years," in May's Amazing Spider-Man #25 and #26, which will also bring artist Kaare Andrews into the title.

So what happened 50 years ago that was so shocking it's now going to be notably matched or even topped by another big event?

For one thing, 1973 (50 years ago) is the year that Gwen Stacy died in Amazing Spider-Man #121 - and considering the looming presence Gwen has had over Zeb Wells' run on the title and its adjacent stories, it seems safe to say that's the 50-year anniversary being referenced in Marvel's announcement.

Marvel has included the covers for both issues in its announcement in a graphic which combines both images along with the phrase "The truth revealed… but at what cost?"

Marvel bills Amazing Spider-Man #25 and #26 as the "startling, unexpected climax" to the current chapter of Wells and Romita's run, and specifies that both issues will be "over-sized."

As for the "truth" that will apparently be revealed, it seems likely it will tie into both Gwen Stacy's death and perhaps the question of "What did Spider-Man do?" which has followed Amazing Spider-Man since its first issue revealed that Peter Parker was responsible for some still unspecified disaster in the recent past before the launch of the current volume of the title.

We know a few things: whatever it is, it's kept Mary Jane and Peter Parker apart and alienated him from others in his life, and it's been hinted that it has something to do with both Norman Osborn and Gwen Stacy.

The story of the disaster will be revealed in the