This is one of Issac Asimov's best novels in my opinon. A detective must leave his over populated world where people live in confined spaces underground. Our hero is agoraphobic and must visit a planet where a world is sparsely populated and very open. The inhabitants of the planet live solitary lives in mansions and are surrounded by robots as servants. When they socialise, they do so via holographic forms. They visit each other only via holograms. They procreate via artificial insemination and can't stand being in the physical presence of one another.
Therefore when a murder occurs, know one knows how to deal with it or how to investigate it. The problem is, our detective needs to interview people, and is agoraphobic too. He can't stand the open spaces. He has the help of an android and must solve the murder mystery and go before people who are physically repulsed by his mere presence. How can these people even get the chance to murder one another?