This is not a book about sex and drugs; the so-called product description is wildly inaccurate.
Up Above the World is the story of two Americans, a retired doctor and his young wife, travelling through Central America and of what befalls them when they encounter another couple, one of whom may be intent upon doing the travellers harm.
I suppose it wouldn't be stretching things too much to liken the book to The Comfort of Strangers but written by someone with the eye of an artist, the ear of a musician (naturally--Bowles was in fact a musician), the prose of a poet and the ability to re-create one's worst nightmare. Bowles excels at depicting landscape, from scrubby plain to dry jungle, and its inhabitants, from crickets singing in the sultry nights to unwordly spiders to inscrutable humans. No doubt that's the reason his books are so full of atmosphere. In this one, the atmosphere from the start is one of menace and doom; I can't convey how oppressively ominous it is but shall say I put it aside for a few moments now and again simply for relief.
It's a shame Bowles seems to be something of a cult writer and perhaps as famous for his life as for his books: he's a far better writer than many more well-known ones. If you've not tried him, he's certainly worth a go--and if you've read and liked this, try The Sheltering Sky as well.