The idea of the books shows promise, but she doesn't help herself by rehashing so much of the first book in the second book and then not leaving herself enough time in the third book for everything she wants to do. It gets really congested at the end and it feels really rushed.
Anyway. I don't think she ripped off Battle Royale. And clearly the original writer doesn't either, or they'd have come up with a plagiarism suit. It's easy to accuse her of plagiarism when you're familiar with Battle Royale, but you need to remember that the majority of people have never heard of it. Why would they have done? At the time Suzanne Collins was writing athe Hunger Games, Battle Royale would have been about 10 years old. It's a Japanese book/film, so not exactly mainstream. Hell, it was subversive and had a troubled release in Japan, before you even think about translating it and releasing it elsewhere. The film had a very limited release around the world and was banned in many countries. It's entirely conceivable that it would pass a huge number of people by.