In the introduction of this book Leopold Lugones is said to be "the initiator of the fantastic short story in Latin America, a forerunner to the masters of the form, Horacio Quiroga, Julio Cortázar, and Jorge Luis Borges." This is an odd collection of writings, from a man who turned from a socialist into a fascist in later life and committed suicide in 1938, something which has befallen several of his descendants numerous times since.
A big theme in these stories is science gone awry, not mad scientists exactly, but obsessive amateur scientists engaging in strange pseudo-science. Another theme is weird apocalypses. Most of these stories have great moments, but this is most interesting to read as a "curiosity" -- you're probably better off just reading Quiroga, Cortázar and Borges. The story "Viola Acherontia" seemed to me an excellent weird tale, rising far above the others. Unfortunately the last third of this book is taken up by non-fiction political essays by Lugones and it felt like I had my appetite whetted by the six stories included, but not quite fulfilled.
The Rain of Fire - This is a grim, apocalyptic tale, with a bit of a decadent flavor as a wealthy man who has retreated from society to become a glutton watches as a rain of fire slowly destroys the city around him.
Yzur - This is a very odd story about a man who believes primates once spoke, but decided to give up that evolutionary advancement -- so he attempts to train a monkey to speak. It seems to be reflecting on the themes of unhealthy obsession and barren scientism.
Viola Acherontia - Wow, this is an excellent story, very much in the weird fiction vein. This story is similar in theme to the previous one, here another amateur scientist is manipulating nature by attempting (through a weird osmosis) to breed a species of flower that will emit a deadly toxin. It is full of insane logic and beautiful prose.
The Pillar of Salt - This one wasn't among my favorites, but still contains some very evocative language and also an apocalyptic theme similar to "Rain of Fire." After many years of a quiet, ascetic life a monk is tempted into releasing Lot's wife.
The Escuerzo - This is a brief but quite decent little horror tale about a mythical creature out for revenge.
The Horses of Abdera - This is an absurdist story, with another apocalyptic theme, and also the same sort of "fooling with nature" theme seen elsewhere. Probably my least favorite story here. A city that treats its horses well, finds the animals growing increasingly intelligent, until one day they rebel.
As for the essays, I read through a few of them but I didn't find them especially interesting. They're fiery political writings of a man who seems to have made a sharp right turn politically. This book would have been better-served by including more fiction instead.