For those of you who are wondering how to begin with Battle Royale, I would suggest to watch the movie first, then the book (the book goes a lot into detail of each character and since the movie lacks that, it would be frustrating to watch first and would mess up your watching experience), and if you really, really insist, the manga.
The story of Battle Royale sets in a dystopian Japan. Censorship and authoritarian violence are common, and not protested - at least not knowingly so. However, unemployment rates soar high and the youth becomes desperate; as they do so, they refuse to attend school, or overall participate in society. This causes the nation to fear collapse. In order to fix this issue, the Japanese government comes up with a dramatic measure called "The Program" (keep in mind that the name 'Battle Royale', besides in the intro of the book, are never used, neither by the author nor the characters), that randomly selects a class of 9th graders and sends them to a remote island where they are encouraged to kill each other. "Encouraged" not "forced". However, if after three days, there is more than one survivor remaining, the collars the students are obligated to wear explode, leaving no survivors at all. In short, it's "to kill or be killed".
IIn my humble opinion, Battle Royale's quality is 50% storytelling. I adored the movie as well as the book, they are my new favorites in each category, and as a big manga fan, I naturally believed the manga would be the same. But the manga took everything that made the book go from "good book" to "cult classic masterpiece that still inspires its genre 2 decades later" and butchered it.
1) The art style contradicts the story
I don't mean that the art style is bad, or that I dislike it. But the main reason why Battle Royale shocked the whole world; the reason why the book was removed from Literary award ceremonies, the movies blacklisted from cinemas overseas, and the Japanese government intervened and imposed an age restriction on the movie against the will of the movie Director, is because of the age of the main characters. Canonically all 14-15, however even the age of the actors cast for the movie are in 14-17 age range for most of them. It's what makes Battle Royale so brutal, besides the violence: it's seeing teenagers who knew each other well and cared for each other at times too, be forced to turn against each other. I read somewhere that in Hunger Games, the children were the victims of the oppressive government: in Battle Royale, they are the targets. I thought it was so fitting. So why in the world do all these characters look 25 at best and 39 at worst? Let's not talk about the oversexualised underage female characters in a book targeted toward an adult, male audience (as most violent mangas are). It breaks the immersion, and more importantly it doesn't make you feel bad for the characters. When you see a 14 year old child being handed a gun and told to kill his classmates, panic and make terrible decisions you feel pity and angst. When that "child" looks like they just graduated medical school your perception changes and you feel like even under such pressuring conditions some of them should've known better. Whether that is true in reality or not, doesn't matter: some of the empathy bonds carefully crafted in the original novel are broken and nothing is done to fix them.
2) The writing becomes "corny" and the original wholesomeness is lost
I have read a lot of mangas. And this sort of corny writing, two characters oblivious to their feelings making weirdly sexual jokes for no reason is no surprise. But really, in B.R, it just kills the mood.
I'll give you a non-spoiler example. In B.R, it is made clear that the Female lead, Noriko Nakagawa, has a crush on the male lead, Shuya Nanahara. We don't have Noriko's point of view, however, so we only see things through Shuya's lense. He is oblivious to Noriko's feelings, as she's never actually tried to flirt with him, or throw "hints". But some small actions she does, caring for him, or blindly trusting him for no reason make the reader understand this from page 2. As Noriko and Shuya navigate together, they feel a sense of care and protection of each other that grows subtly, without ever notifying the reader. I think one of the main reasons why I liked B.R so much, was because the romance was not overbearing. It was not slow either. It just didn't appear under the form of "lust", or infatuation: their love (and that, ironically sounds corny) came under the form of trust in a game specifically designed to make you distrust everyone including yourself. It's what's so amazing about their romance: and not that they just put the two good-looking characters together because they happened to look. Shuya even mentions several times in the book that he never noticed Noriko because while she's not ugly, there's many pretty girls in the class and in comparison she's average. He even describes his type at some point; which is the direct opposite of a girl like Noriko. You get what I'm trying to say?
Now what did the manga did with this? Like in the movie and book, Shuya asks at the beginning how come Noriko trusts Shuya. And she replies "because you didn't look at my panties." Then indirectly confesses to him, and Shuya says "wow... one of the prettiest girls in the school watches me." And so they become this power couple where Shuya promises himself to protect her, and she, the useless damsel in distress who follows along. As I said, Battle Royale is in many aspects quite predictable and cliché (including the dynamics of the main characters), but the reason why it's amazing is the storytelling!
3) Mitsuko Souma
Mitsuko Souma was and still is my favorite character of the story because of her complex persona that is brought up several times by other characters in the book. The justification of her actions different characters find is interesting, and its opposition to the "one who is like her", despite having similar actions, is in my opinion what makes the book eventually reach its climax.
Mitsuko Souma says "I was just tired of losing" and her entire character, that varies from a strong, unstoppable wave to a vulnerable child makes everyone uneasy, including the reader, because she is so unpredictable.
So I am absolutely appalled and disgusted, and it's why I'm giving this manga a 1-star, about what the manga did to her. A 14 year old victim of the adults and the horrible system who failed to protect her, painted in a clever way, only to get turned into a hypersexualised shell of a woman (and i mean 'woman' not girl) whose backstory and identity have been only used to further her sexualization (which is oddly, exactly what fictional Mitsuko fell victim too.)
I'm not sure whose idea was it, to turn every kid into a raging sex maniac with complete disregard to other people's lives turning them into these cruel killing machines, but it made the reader lose one important thing: empathy. Who cares if that boy died? He killed all those people and enjoyed it. Who cares if this girl was killed? She was trying to kill others first and that's well deserved. The thing with battle royale, is that whether human beings do good or bad things (because in B.R, they WILL do both) they are STILL human beings and the entire point of the story is to put an emphasis on that. But in the manga, they are mere meatbags dying for the sake of the characters who "matter" to progress throughout the story.
The story is amazing, it's just the quality of the writing and pacing in the manga is poor. Think I'm being dramatic? Here is the line of one character from the book, and notice how the manga changed it. Ask again if I'm dramatic after reading.
Book: "Hey it's (Character1). I just wanted to remind you (Character2), to turn off your cell phone. Otherwise, if I call you like this, everyone will know where you are, right? So..."
Manga: "MMM... What are you wearing, young muffin? Daddy misses his peak of pink... Yes, he does. Your turn, young missy. Tell me something I can masturbate to, hmmmm? Izzum's daddy's widdle girl?"
The character is completely changed into this for NO reason: he is NEVER like this in the original story, nobody is. Yes, it's okay to change things during adaptation, but to change the story into some weird sex-gore novel is weird. I see many people recommending the manga instead of the book/movie and I just felt the need to write this. You can read the manga, enjoy it, but my recommendation is to try the others first.