Stop ruining books!

Woah, I have this in my drafts since September, how did that happen? I have some ideas, but either way, I think it gathered enough dust and it is about time I post this. But first let me just mention from that start that I am not yelling at the authors here. There are a lot of different topics and genres and unless the writing is absolutely awful, anything goes as far as I am concerned. Who I am yelling at is the readers, but more accurately the ones of us (yes, me included) who write opinions or reviews on various sites after reading a book. And I am so mad at some of the reviewers. I have pretty good reasons, too, I'd say. At least me concerned. 
First of all I must mention that I was never a fan of spoilers. Actually, I outright can't stand them. If it is about something I am interested in, the moment I see a spoiler my interest goes to mush. Sometimes, if enough time goes by, I completely forget about it and get interested in that particular book again, b...