Aldous Huxley's Brave New World. It's a must read if you're into dystopia. Unlike Orwell, Huxley doesn't focus on politics of his time. Specially good to read alongside Island, an utopia of the same author, dealing with similar topics (society, drugs, the human condition).
Anthony Burgess' A Clockwork Orange. It has some satirical vibes, but it is not a good book to read if you're feeling down (content warning: sexual violence). It focuses on a teen gang leader in the near future, and talks about themes like the impact of free will on morality.
William Golding' Lord of the Flies. Technically not a dystopia, but it "scratches" the same itch. It's about a bunch of kids dumped in an island, without adult supervision, and the resulting nasty proto-society that they build from it.
Yevgeny Zamyatin's We. It's perhaps one of the grandparents of the genre; it talks about individuality on a society controlled by a state that managed to conquer the whole globe.
There's also Ayn Rand's Atlas Shrugged. I don't recommend it - the book is basically a "if Orwell was right-wing, soapboxing instead of trying to explain what's going on, and with poor writing skills". Seriously.
Yeah, the whole book boils down to "the hand of the market will solve errything!". Except that Rand doesn't know that the hand of the market has Parkinson's.
She also kills off every character she sees as weak through their generosity. The book just hits you so hard over the head with her philosophy rather than letting you think.
Fuck. How could I forget mentioning it? I love this book, and the political implications of the story - with powerful States being nuked into mutants, and the little NZ in the middle of nowhere, completely forgotten, is saved by its own lack of relevance. The whole idea of a story within another story, with non-human apes doing human activities (to drive the idea that we are behaving like the other apes too) was genial.
No problem. I'm glad you liked it as well. I definitely read it right after brave new world around high school age. I should really re-read it. It's been a long time.
I dont know why I could never get through brave new world. I tried reading it once when I was in my early 20s and tried the audio book this year and couldn't do it.