Ursula K. LeGuin is one of my favourit writers. And I'm saying writer and not SF writer as I think Ursula uses SF as a way to transmit all her philosophical views about life and human behaviour.
"The Dispossessed" is a master work. In this book, Ursula raises a conflict between two societies. The one which could be our own society, a world moved by the capitalism, the money, the power...The other society is an authentic comunist society, where there are no ownerships, and utopically means the perfect society. Ursula tries to show how this utopy can't be achieved by the human beign due to its own human condition.
This is a really "must read" book.