Selection of detail in literature refers to the details that the author reveals for the purpose of adding to the desired dominant impression. These details are selected based on what they tell the reader about the person, place or thing being described.
In the written form, the reader can only see what the writer chooses to reveal, so the reader may infer inherent importance of any details the writer shares. Extraneous observations or descriptions reduce the focus on important details, which can water down the impact sought by the author. When examining literature, the details that are revealed give the reader some insight into what the writer found important about the passage.