This is part of a series I loved in my teens that was published from the 1970s through the 1980s, and I don't believe any are in print. I find that a shame. Though I wouldn't count this a deathless science fiction classic featuring an awesome prose style such as that of say, Ursula LeGuin, it's one I enjoyed in the same way as books by Marion Zimmer Bradley or Anne McCaffrey. As good, solid action/adventure, often featuring romance and imaginative world-building. So this isn't rated so highly because it's groundbreaking science fiction in the same league as Asimov or Heinlein. I'm rating it so high because this is favorite comfort food reading, with characters I love. I own eight of the Sime/Gen books, all I could track down after reading the first one, and of those eight, this one, Ambrov Keon, is my favorite.

The premise of this book is that in the far future humans have mutated into two different types. One kind, the Sime, feeds on the energy of the other kind, the Gen. But this mutation--or possibly genetic manipulation, erupted suddenly and violently, with Simes going through a change at adolescence in which they gained tentacles allowing them to rip the energy from Gens--causing death. And their cycle means they have to do it every month.

As a result, civilization collapsed and reemerged split into two sides. In the Gen society, when some adolescents change into Simes, they're immediately killed. In Sime society, if their energy settles into Gens, they become slaves and food. And parentage is no predictor. So parents raise children knowing that one way or the other they could lose them, see them become monsters or cattle.

But things have begun to change. A Sime and Gen, in love, discovered that certain Simes, called Channels, could take this energy safely and transfer it to other Simes. And certain Gens, called Companions, could control the transfer of energy so both could survive.

Enter Risa Tigue, born into Sime territory and trained to think of Gens as not human--until she meets Sergi, a Companion who changes her life. Risa is the primary reason this is a favorite. She's that oddity in science fiction, especially when this was published in 1986, a strong female character, a leader. It occurs to me her name is similar to FM Busby's Rissa of Rissa and Tregare, another strong female figure in science fiction from decades ago, and I suspect the name might be homage, because I can see a lot of similarities in their spirit, and in the entrepreneurial drive both share and which Risa uses to help transform things around her. ( )

In the far future, the human race is divided into Sime and Gen, just as it is into male and female. Simes must take energy from Gens each month to live, but when they do so, the Gen usually dies. Can they learn to live together without killing before the human race is destroyed? ( )