Alternate Realities: A Scifi Book Club discussion

I have heard criticism that Battle Royale isn't technically scifi but more of horror novel. What do you think?

I haven't read the book, but I think any "world" that has such a dystopian premise accepted by the governing class qualifies as science fiction. A particularly gruesome sub-genre, sure, but science fiction nonetheless.

Can't wait to get my hands on this book, I've watched both movies and also wanted to read the manga, but I'd like to read the novel first.
I guess it's dystopian sci-fi, like The Hunger Games, which many people consider a rip-off.