Blurbs
Imagine, if you will, a future in which I'm editing an anthology.
Now imagine that for some reason beyond human ken, in writing the little about-the-author and about-the-story blurbs that precede each story in this anthology, I decide to offhandedly remark on the details of the central surprise revealed in the climax of the story.
I hope that should such an unfortunate event come to pass, someone will have the courage to take away my computer before things get out of hand.
Luckily, I long ago learned the trick of avoiding reading such introductory material until after I've read the story. I learned even before that to avoid reading the Introduction to an anthology; most of the time those don't contain spoilers per se, but they do usually contain more of a thematic description of each story than I want to know in advance. But that's a publishing convention—the Introduction is designed to tell you about the anthology, of course, and sometimes to convince people browsing in a bookstore to buy it—so I expect it and it doesn't especially bother me. But I just read a story in a science fiction anthology, and then went back and read the about-the-author-and-story blurb, and at the end of that blurb the editor very explicitly and directly says "This [is a] story in which [X does Y] to ensure [Z]" where Y and Z comprise the surprise that's at the core of the story, not revealed until a couple of pages before the end. It's possible that it wouldn't be a surprise to people who'd read the author's other work set in the same universe, but I haven't, and it would've ruined the story for me if I'd read that blurb.
It's even worse when the blurb gives spoilers that are incorrect—the previous story in this anthology has a blurb that describes a background event that I'm pretty sure didn't actually happen in the story.
Grumble grumble when I'm in charge grumble editors grumble spoilers grumble let the story stand on its own grumble grumble.
In unrelated and much better news, I think I got upwards of 8 hours' sleep last night, for the first time in some weeks. Very pleased.