Love it! We don't see old school sci-fi so well written often! A very atmospheric writing, poetic even at time. A concept that's now well known but in 1967, this was something quite original! Yes it's officially science-fiction, but we get element from mystery, even an horror vibes in the beginning and some sort of weird love relationship. Amazing variety in the narrative, strong ideas and an intriguing premise. Classic science-fiction doesn't get a lot better than this!