There are any number of literary elements to choose from in "House Taken Over," but I can outline a few of the major ones here.

Perhaps the simplest is that Cortázar uses a first-person point of view: the story is narrated by someone directly involved, an "I" who tells the story.

The entire story can be considered an allegory for Peronism, or a form of Argentine populism. The narrator and his sister are representatives of the Argentine bourgeois class: they are idle most of the day, with money coming in from land rentals; the narrator reads French novels; there are only two of them but they live in a huge house; they take up more space than they need, in a family home that they did not earn, but rather was passed down to them. And yet their wealth and their space is being taken over by something (allegorically, the populace, the working class), cutting them down to size and leaving them with nothing. The line "Irene never bothered anyone" is critical within this reading of the story: she was minding her own business. She never went out, never contributed to society or the economy—the narrator did those things, and only rarely. The narrator is painting Irene as a victim of the working class's takeover; she loses everything, which is then presumably divided up among those who could not afford it.

On a less political note, Cortázar also uses suspense and foreshadowing to keep the reader on their toes: we never see what it is that is taking over the house; we only know that once they have invaded, there can be no going back. When the narrator first hears them,

The sound came through muted and indistinct....At the same time, or a second later, I heard it at the end of the passage which led from those two rooms toward the door. I hurled myself against the door before it was too late and shut it, leaned on it with the weight of my body; luckily, the key was on our side...

In this scene and the last are the only times we get a sense of urgency on the part of the narrator; he "hurled" himself against the door "before it was too late." The pace is quick here, and the sudden eruption of the existence of this "other" in the house leaves the reader with a suspenseful, ominous sense for the rest of the story. The "other" taking over this part of the house also foreshadows the taking over of the entire house at the end of the story.

The last element I will mention is the motif of collecting or gathering in the story: motes of dust "rise and hang in the air, and settle again a minute later on the pianos and the furniture." The siblings' income from the farms was "piling up"; Irene has hidden stacks of shawls in a drawer; and when the narrator finally flees, he abandons a large stack of money in his bedroom. This could be read (but is not necessarily intended) to be an indication of the wealth amassed by the middle class and the sheer amount of things amassed in capitalist society, despite their relative idleness and lack of need.

Julio Cortázar employs Magical Realism and Gothic techniques in his short story "House Taken Over":

• Magical Realism (elements are in italics)

--One aspect of the story that might be identified as "realist description" is the portrait of the house in which the narrator and his sister dwell—it has been owned by generations before them and the siblings love it because it holds memories of ancestors and "the whole of childhood."
--Another aspect of Magical Realism is that time is "both history and the timeless" with the historic ancestral home and the occupancy of the siblings, who have both lost their opportunities to marry. They then seal themselves from time with their reclusive routine of cleaning the house and spending the rest of the day occupied with favorite pastimes of knitting and reading.
--The reader is torn between two concepts of reality. Apparently, there is a supernatural force that enters the house, but the brother, who narrates, describes the take-over of the house as though it were not unusual:

I'll always have a clear memory of it because it happened so simply and without fuss....The sound came through muted and indistinct....At the same time or a second later, I heard it at the end of the passage which led to those two rooms toward the door....

--After hearing these noises, the brother calmly goes to the kitchen, heats the kettle, and when he returns with their daily maté, he tells his sister that he had to shut the door to the passage. "They've taken over the back part" he says, apparently assuming that his sister knows who "they" are. There are two realms of reality.
--The siblings have their identities "broken down" as they surrender the house to the spirits and give up some of their favorite possessions. With an odd passivity, the brother and sister reside in their part of the house. Finally, when they hear noises in the kitchen and other areas which they usually occupy, they abandon the house without a word to each other or without even taking anything with them. Passively, the brother locks the front door tightly and throws the key into the sewer. He narrates with this same passivity:

We had what we had on. I remembered fifteen thousand pesos in the wardrobe in my bedroom. Too late now.

• Gothic Techniques

--There is definitely a mysterious atmosphere to the house of the brother and sister.
--There are supernatural occurrences as the house becomes occupied by some type of spirits who move about and cause the brother and sister to run from them.
--The elements of gloom and horror are present as the brother and sister fearfully hide in the other part of the house where they are trapped and without the items they love. Then, after the brother hears the spirits on their side of the heavy oak door,

We stood listening to the noises, growing more and more sure that they were on our side of the oak door, if not the kitchen, then the bath, or in the hall itself at the turn, almost next to us.

So they must flee part of their house in fear of the spirits that have taken it over.