Connor's Thoughts

Say you and your friend were reading a book. Now say you finished the book before you friend, and told them that it had a twist ending.

Now, would this be grounds for a spoiler? Would your friend have a right to get angry?

Could you really not see a twist ending coming? I mean, not from the story, but since so many books seem to have them nowadays?

And when will it get so bad that it's surprising when the book doesn't end on a twist ending?