Overview
The story is set in a portion of the galaxy populated by fifty-two different sentient species. All of these species, humanity among them, have evolved in the last five million years, and all of them have evolved in a spherical volume of space only a few dozen light-years across centred on Wolf 359. The rest of the galaxy is sterile as far as anybody can tell.
Scattered irregularly across this "life-bubble" are ancient artefacts of a mysterious race called the Jokers, who became extinct long before any of the current races arose. These artefacts are usually astounding feats of engineering (such as a pair of stars shaped into rings and joined together like links in a chain), but leave no hints about the Jokers' physical form or day-to-day life. The only piece of translatable Joker text is a poem, which cryptically states that they have gone to their new home, which "lies at the dark side of the sun".
Read more about this topic: The Dark Side Of The Sun