This story is revolting. Child abuse is an issue that many real people actually face and that most authors at least try to approach with a certain degree of sensitivity and realism. This author, on the other hand, is depicting brutal assaults and torture as a crass technique to manipulate the reader's emotions. It's there purely for shock value, to add artificial tension to what would otherwise be yet another high school bad boy romance. Yes, it's poor writing, but it goes beyond that and into the realm of the offensive.
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My constructive advice for the author is to delete the story and not revisit sensitive topics such as these until you're able to approach them with a more mature attitude.