The novel's protagonist, Ny Axxter lives on this wall and tries to make a living as a freelance artist working with video and graffex. One day, he has what appears to be a stroke of good fortune and he thinks that he is on the verge of making it into the big time as a major artist.
At this point, his world starts to fall to pieces and he discovers that reality is not what he, and everyone else thought and that the major players in his world now want him out of the way.
While many parts of the world are unexplained, Jeter throws in enough in the way of technical details to make this hard SF and not fantasy. The writing style is very sharp.
Jeter is regarded by many as an heir to the mantle of the great P.K.Dick and this book is worthy of that regard. I always think that a sign of good writing is the quality of the pictures inside my head as I read and, on the measure, this was very good indeed.
Farewell Horizontal is a gripping read and I highly recommended it.