It is a drama (a play). Apart from school readings, I have never read such literature myself.
The author is known for atmospheric horror novels written in the style of Edgar Allan Poe. He uses a peculiar and old-fashioned language (he wrote his books at the beginning of the 20th century). The characters in his novels often hide secrets, have a past related to the occult or supernatural phenomena.
The plot focuses on the discussions of the main characters about their unhappy marriage and past events. However, elements of the occult appear and the tension associated with it increases.
It was a really enjoyable read, although very short (less than 50 pages).