I don't think anything needs to be said about Franz Kafka's
The Trial. A book that can be read on so many levels. Whether you read it as the state gone mad or the paranoia of one individual it is equally effective.
Many point to Kafka being a one-trick pony, but that should not take away from the genius of that pony and this book. It'll club you over the head and drag you kicking and screaming until you believe it still can and will happen in our society.
Just reading all the comments on Nancy Drew should make one realize that the best book is obviously the one that points at the madness of bureaucracy.