Jacqueline Lichtenberg’s 1978 Unto Zeor, Forever is either the 6th Sime/Gen novel or the 2nd, depending on whether one goes by internal chronology or by order of publication.
Digen Farris heads off to a medical residency. This conventional tale of a well-meaning would-be surgeon is complicated by the fact that Digen belongs to what some might deem a genetic aristocracy and others a terrifying lineage of soul-eating vampires.
Humanity is no longer the pinnacle of evolution. In a burst of pure orthogenesis, humans have divided into two subspecies: the Gen, who can provide life energy (known as selyn) and the be-tentacled Sime, who need to consume selyn. Marring this ideal symbiosis: should Gen inexplicably experience fear while having their life-force drained, the Sime draining them will go into a murderous frenzy. Not only will the Gen die but the Sime will henceforth be an obligate deranged killer1.
The Tecton imposes on its member communities strict rules designed to ensure the bad old days of open Sime/Gen war never return. Just as Sime can be seen as superhuman or horrifying monsters depending on one’s point of view, so too can the Tecton be seen at the only thing standing between Sime/Gen and bloody chaos or as a collection of obstructive bureaucrats enforcing rules in blind disregard for the original intention of those rules.
Digen’s professional interests could easily bring him into conflict with the Tecton, in particular with Controller Mickland. It behooves Digen therefore to keep a low profile. However, while Digen has many positive qualities, subtlety is not among them. As he befriends Gen and puts his peculiar talents in service of medicine in general and surgery in particular, it is only a matter of time before Digen violates convention in some sufficiently visible way that the Tecton will have to take notice and act.
Luckily for Digen, there are those who see the Tecton as a tyranny. Digen could look to them for refuge. Less luckily, these particular freedom fighters are hard-core Social Darwinists who, if they have their way, will trigger the deaths of millions and the collapse of civilization as the Sime/Gen know it.
The Sime/Gen books were popular in the 1970s, and I used to see copies everywhere. I never read them then; this is my first foray into the series.
Book 2/volume 6 may not be the right place to start. The reader is presented with a flurry of unfamiliar terms to absorb (modern readers may wish to resort to the wiki). Perhaps Book 1/volumes 1 through 5 eased readers into the setting more gently. It’s clear from the text that the author has a very clear idea what’s going on. Some readers — this reader, at any rate — may be less enlightened.
While reading this I was reminded of Octavia E. Butler’s Patternist series. Given that the two series were published more or less simultaneously, the parallels are almost certainly purely coincidental. The significant thematic difference is that Butler was a much better writer and considerably less sympathetic towards psychic vampires than is Lichtenberg. Imagine, if you will, a reimagining of the Patternist books as hurt/comfort BDSM.
The ongoing popularity of the series suggests that some readers find this a richly imagined setting for compelling adventures. I experienced this book as tediously contrived to result in the sort of overwrought emotional and bureaucratic conflicts the authors2find interesting. Reading the novel, I had the sense I was observing an enthusiastic celebration of a kink I don’t share. Definitely not my thing but if it is yours, copies are easy to find.
1: To make matters worse, a third of Sime children are Gen, while a third of Gen children are Sime. There is no way to avoid Sime/Gen contact and potential conflict.
2: Some of the novels were written or co-written by Jean Lorrah. The series also supports a rich ecosystem of authorized fanfiction.