I first read Golden Sunlands soon after it was first published in 1987 and enjoyed it enough to keep on my shelves, so I recently decided it was time to enjoy it again.
The time is the distant future, with humanity spread across many star systems. On the remote and rather primitive world of Calabel, the human inhabitants are going about their affairs when they are suddenly scooped up by robots emerging from a fleet of spaceships. These return to a huge mother ship which spirits the entire population of the planet to an artificial universe in which a vast number of red dwarf stars are arranged in a symmetrical pattern, each providing light and warmth to its own flat discworld with a surface area millions of times larger than a planet. These are the golden sunlands of the title.
The humans gradually discover that the humanoid Golden Iulliin, the ruling race who created the universe aeons ago, while still very much present have lost their knowledge of the technology and in some cases reverted to a medieval level of existence, with ancient ruins scattered about the sunlands. So far the setting is reminiscent of Niven's Ringworld but on a much larger scale, and indeed anyone who likes Ringworld would probably enjoy this. Events soon take a different course, however. The iulliin are still obeyed by their slave races; the ferocious yashi, reptilian dagbabi and the siffile - their name for humans. For the inhabitants of Calabel were not the first to be captured; another human world had been similarly emptied millennia before and their descendents were still around.
Almost all of the humans find themselves rapidly processed and brainwashed to become soldiers in an endless war between two of the sunlands. A handful manage to escape in one of the smaller spacecraft and land on a different sunland, where they are captured by primitive iulliin and threatened with ritual sacrifice. The two groups face a wide variety of adventures and problems in dealing with their equally threatening situations while trying to understand the nature of the universe they have arrived in.
Although I have to admit that I wasn't quite so impressed on this reading, it is still an enjoyable ride through a fascinating invented universe with some very varied and credible characters (human and iulliin). However, there is one major drawback which I had forgotten - it ends mid-flow, with most of the issues unresolved. As far as I can tell in a web search, no sequel was ever published. This is a pity, since I would love to see where the author was planning to take this story and would certainly buy a sequel. He is still writing, but appears to have switched to fantasy rather than SF.