Battle Royale II is not one of the worst movies ever, it's a good sequel to a frankly amazing original.
Yeah it's got some cheesy scenes in, just like the first one, but it's still worth the look if you enjoyed the first one, even to see Beat again. The first part of the film where they are getting all their weapons and stuff in the sequel is great, I loved the acting from a boy while holding an american football.(will not say anymore, you will know if you check it out)
The first film is adapted from the novel.
I have seen the manga books, have lots of the books in a shop near me.