I guessed wrong, again, with And Then There Were None

I read a lot of mysteries and I'm annoyingly proud of solving them early. Not this one. I had three different theories and all three people died.

Ten strangers on an island and a poem that tells you how they'll go. That's the whole setup, and it's so simple that you assume you've seen it before. You have, because everyone copied her. No spoilers here, but read the ending somewhere quiet. And don't look anything up beforehand.