As a slightly different take I'd recommend SS-GB. Technically it's an alternative history novel whether the Nazis won WWII and conquered the UK.... But that's pretty dystopian in practice, especially when the main character is a policeman.
I don't know if The Trial counts exactly as a dystopia but it certainly conjures up the paranoia and confusion of being caught up in a beruacratic nightmare like you might find in a police state.
High Rise is a great satire on the class system translated to people moving into the then new high rise blocks in the UK - only the rich can afford the apartments at the top and so on. The first sentence involves the hero having to eat a dog to survive.
A Clockwork Orange has been mentioned already, but it's easily my favourite. And very different and more brutal than the film, which is also great but more its own thing. Alex is a much nastier piece of work in the book, and the last chapter of the novel isn't in the film