I believe that "The Moon is a Harsh Mistress" is the best Science Fiction books ever written in the category of "Not part of a trilogy". A couple of asimov's robot books, and Dune repersent close seconds ("trilogy" came much later) in that category. I would love to hear your other candidates.
TANSTAAFL, I was always under the impression, came from the book, but perhaps it appeared in some earlier work.
I did mostly "classic" SF in the course, plus a few later novels that moved the genre. Here are books from the last few times I gave the course:
Robert Heinlein, The Moon is a Harsh Mistress
Asimov, Foundation.
Arthur Clark, The City and the Stars
John Wyndham, Day of the Triffids
Ray Bradbury, The Martian Chronicles
Walter M. Miller, Jr., A Canticle for Leibowitz
Frank Herbert, Dune
Robert Silverberg, Downward to the Earth
Samuel Delany, Nova
Philip K. Dick, Do Androids Dream of Electric Sheep\
Ursula LeGuin, The Left Hand of Darkness
Larry Niven, Ringworld
Piers Anthony, Macroscope
Gene Wolfe, The Shadow of the Torturer
J. G. Ballard, Empire of the Sun
William Gibson, Neuromancer
Some years I would do different books just to take a rest, such as Kurt Vonnegut's Player Piano, or Kornbluth and Pohl's The Space Merchants.