This is probably my favorite manga right now. They set up the deaths of each kid with a little back story first so it actually hurts when some of those kids go. Even the bad ones. Some of the kills are just brutal, not so much for the violence and gore (and boy is the violence and gore there) but for the situation they happen in. This manga hits hard. There is even a hentai volume as a bit of fanservice.
Well, not the whole volume but a lot of it and a bonus sidestory.
The movie is good way to kill a few brain cells. I suggest watching it with friends so you all can laugh together.