The novels already mentioned are great. I would add:
Brave New World by Aldous Huxley
Sons and Lovers by D.H. Lawrence
1984 by George Orwell
Animal Farm by George Orwell
The Prime of Miss Jean Brodie by Muriel Spark
Lord of the Rings (trilogy) by JRR Tolkein
Dune by Frank Herbert
My Antonia by Willa Cather
Pincher Martin by William Golding
There are so many great novels....... hard to create a "short list". Keep in mind that I'm a socialist and I also like speculative fiction, so my preferences are skewed in those directions.