Set on a future Earth where the majority of the human population live in cavelike gigantic supercities. The very concept of stepping outside, to have nothing above your head but sky enough to fill the average citizen with feelings of panic. The small minority who don't live on Earth in these cities are the Spacers, citizens of the 50 human colonised planets, for whom the Earthbound civilisation harbour string feelings of resentment and even hatred.

Adjoining New York City is Spacetown, the Spacer maintained city allowing interaction between Earth and its colony worlds. A man is killed in Spacetown and it is suspected that an Earthman is responsible for the murder. But to have done this would mean that the killer would have had to trek cross country to not be detected at the border, and unthinkable act.

New York Detective Elijah Baley is assigned to investigate the murder and is partnered with a Spacer Robot R. Daneel Olivaw. He sets out to find the killer and prevent an incident damaging to Earth.

This is a novel I first read in my early teens, longer ago than I really like to consider. It's the first of Asimov's Robot novels and after all these years I still find it a wonderful read, unlike some of the experiences I have had rereading books favoured in my youth.

There is a lot of depth in this novel, despite its relatively short length. Asimov's future Earth is wonderfully realised, the horror evident in the reaction of the Earthbound is superbly realistic, the social conditioning imaginative and self consistent, the anti-robot and anti-Spacer sentiment handled well without any over-the-top theatrics.

Okay it is fair to say that Isaac Asimov is one of my favourite authors, but I think that this should appeal to most SF fans. His writing style is wonderfully simple and clear, without overly descriptive prose or awkward construction getting in the way of a good murder mystery.