From the Biblical "Writings" (Or, More Simply, a Short Story)
Like Daniel, Esther is an example of a short story from the ancient Hebrews. It's one continuous tale, as well. Whereas Daniel is comprised of a bunch of different stories (all from the lives of Daniel and the people associated with him), Esther sticks to the same narrative. But does it fit into the Hebrew Bible's big narrative: the story of how God guides the Jewish people through history?
The "Writings" or "Ketuvim" make up the third section of the Hebrew Bible, and people typically believed they were written under divine inspiration (though they weren't quite as inspired as the Prophets). So people usually interpreted Esther as having some deeper religious meaning, looking for the workings of God behind what on its surface seems like a Game of Thrones-style tale of court intrigue.