Farewell Horizontal is a potentially dazzling post-apocalyptic SF concept that is sadly short-changed by K. W. Jeter's decision to turn it into a simplistic actioner that leaves loads of missed opportunities pounding at the door. The novel takes place both inside and outside an enormous structure called Cylinder, which we are led to understand houses perhaps the entire human race in the centuries following armageddon. Ny Axxter is an artist who specializes in graffex, which are basically fancy logos for the numerous military clans that live both inside (horizontal), but mostly on the outer surface (vertical, you see) of Cylinder. These military clans apparently run the whole show where Cylinder is concerned, and the inhabitants inside Cylinder treat them with the same sort of fandom we today reserve for our favorite sports franchises.
The reason you see me using terms like "apparently" and "led to understand" is that Jeter singularly fails to provide us with a solid understanding of just what kind of society exists in Cylinder. We get an indication that its commerce is based primarily on information exchange, with fortunes rising and falling based upon which of the military clans is whipping up on another more successfully. And we know there are tons of malcontents either living as "circuit riders" on the inside, mucking around with dataflow, or simply living like Ny on the outer surface of the building, traveling the miles of cables that run all along the immense walls. (Though we get the impression that Ny is pretty high up, he never seems to need any oxygen apparatus.) But we never really understand why they are malcontents, nor what they have to be malcontent about. There's no background whatsoever provided on how Cylinder came to be, or what day-to-day life is like for its horizontal inhabitants. As for the building itself, Jeter tantalizes us late in the novel with the promise of satisfying our curiosity. One character tells Ny, "Cylinder was built for a reason...you gotta ask why they bothered." Sure, but the follow-through never arrives.
Fortunately, Jeter's knack for action storytelling does give the novel a readability and an energy that helps us, at times, to enjoy ourselves and overlook these little gaps. Ny is barely scraping together a living on the outside, making videos of the rarely seen "angels" (humans who were genetically engineered ages back to float through the air with big gasbags on their backs — why? don't ask) to sell to the entertainment-obsessed populace. Ny's agent one day turns him on to a potentially swell deal: the biggest and most powerful of the military clans, Havoc Mass, want new logos, and want to use a freelance graffex artist rather than the conglomerate they've been using in the past. Ny is being offered the job because Havoc Mass apparently liked the logos he did for another clan whose asses they kicked at one time or another.
To cut to the chase here, everything goes horribly wrong. Ny discovers he has been set up. Havoc Mass's biggest rival gang, Grevious Amalgam, is prepping for all-out war, and Ny finds himself caught in the midst of their power struggle as he flees for his life across, and finally through, Cylinder.
The story makes sense, such as it goes, and is fun to read. But ultimately it frustrates, and not only because of the huge gaps in backstory. As the tale progresses, Jeter begins resorting to plot devices more and more until the novel begins reading more like a rote exercise. Two characters turn up late in the story, for the sole purpose of helping Ny through his plight. Indeed, they not merely help but actually start making his decisions for him, so that Ny ends up as a passive participant, a supporting player in his own story. And most disappointingly, the "angels," a promising story element and Jeter's most intriguing and original concept in the entire tale, are finally revealed to be nothing more than a plot device themselves. An angel Ny rescues from death early in the story turns out to be the one means by which Ny can get a desperate message for help sent out precisely when he needs to.
There are enough good ideas here that Jeter really could have turned Farewell Horizontal into a novel that was as intellectually challenging, and curiosity-satisfying, as it is viscerally entertaining. That he dropped the ball when it came to letting the story do full justice to its premise and concepts is a disappointment.