The Best of Trek
has a fascinating article by Leslie Thompson about the Klingon homeworld and culture. Published in 1974 it long pre-dates what we learned (and what was changed) about the Klingon Empire and their world in the movies and subsequent Trek series. It's a fascinating read. I wish a similar article speculating about 23rd century Earth had been published.
What do you think future-Earth would have been like if they'd visited during The Original Series? Much like the Earth of 1966-69, or something completely different? Is the version you imagine while watching TOS anything like what we saw in The Motion Picture, or Roddenberry's earlier Phase II concepts, or even what we see in the Star Trek Into Darkness trailers?