Really hate summaries on the jacket that give away spoilers even more so when it is a mystery. Like thanks summary I didn't really intend to read the book or anything :/
It really, really bugs me too. I mean, I get that people have a different appreciation of they think a spoiler is, but I hate it when I get told major plot outlines in mysteries...or any other novels.
Personally can still enjoy a book even if spoiled somewhat.Will say,though, it is still disappointing if the summary hints at any sort of spoiler especially if the book is meant to have a big plot twist like so many mysteries and thrillers tend to. Due to this I tend to sometimes not even read the summaries for mysteries and thrillers just to stay in the dark.