Norstrilla, by Cordwainer Smith

It is one of the enduring tragedies of science fiction that the man who wrote as Cordwainer Smith died so young. His life was weird and fascinating - from living in China during the revolution to writing what is still considered to be one of the fundamental texts on psychological warfare - and his experiences with such a variety of people and cultures comes through in his stories. He takes perfectly believable aspects of people and twists them so far out of proportion that they are barely recognisable in order to show them in high relief - like the Norstrillans in this story, who are the wealthiest people in the known universe by orders of magnitude, but deliberately keep themselves in a simple lifestyle by imposing an import tax of 2 million percent on everything coming in to the planet. Or people whose lives are so perfect they have no challenge, so they deliberately re-introduce accidents and disease to their world to keep things interesting. He also tackles (in one of those strange coincidences of unknowingly reading two books about the same theme back-to-back, which seem to happen to me inordinately often) the same sticky question of how immortality would change human society that Elizabeth Moon was delving into in her Serrano books.

This is a story which describes a young man who buys the earth and goes to visit it, becomes a cat, meets some people, and goes home. Thats not what its about, but thats how the story goes; to remember what its about you'll just have to go back and read it again - I can't imagine summarising it in any way that wouldn't do it an injustice.