"作家が自己ではないものを想像し、見知らぬものを親しませ、馴染みのあるものを神秘化する能力は、その力の試金石である。"

Simplified Meaning:

Good writers can make us understand things that are very different from our own lives and experiences. They can take something unusual or unfamiliar and make it seem normal and easy to relate to, like a good story about life in outer space that makes us care about alien characters. Conversely, they can take everyday situations and make us see them in a new, exciting way, like describing a simple walk in the park that suddenly feels magical. This skill shows how talented a writer is. So if you want to know how powerful a writer is, look at how well they can make you feel connected to things you never thought about before or make ordinary things feel extraordinary. For example, a great writer can make the emotions of a king in medieval times feel just like our own, or they can take a boring bus ride and describe it with such vividness that it feels like a grand adventure.