Which of the following accurately describes an epistolary novel?

An epistolary novel is characterized by its use of letters, diary entries, or other forms of correspondence to tell the story. This format allows readers to experience the thoughts, feelings, and perspectives of the characters directly, as if they were reading their private communications. This immersive quality can provide depth to the narrative and create a sense of intimacy between the characters and the readers.

The other options do not capture the essence of an epistolary novel. While incorporating illustrations might enhance certain types of storytelling, it does not define the epistolary form. A focus on poetic form describes a different genre altogether, and a collection of short narratives would not have the continuous development of characters and plot typically found in an epistolary novel. Thus, the correct answer accurately identifies the defining feature of this literary genre.