The phrase focused and narrowed makes me think of a laser light; as the light gets focused, the spot becomes more narrow.
When the phrase is used in literature, it's often used for something more abstract, like a person's concentration or attention. When our minds block out other distractions, our attention becomes more narrowed and focused on the problem at hand.
As for this passage, it's hard for me to imagine how the "darkness of space" can become more focused and narrowed – unless it's trying to describe a shadow in the dark? It's a rather surreal passage, and I don't believe that a better grasp of English would give you a better understanding of what the author has written.
So, what does it mean? It might mean that it's time to find a more understandable book to read.