Using noun phrases to build worlds

How do writers use language to create images in your mind? Read this extract and think very consciously about the kinds of images the language is conjuring up for you.

A rustle in the tunnel darkness; the knife was in his hand, and then it was no longer in his hand, and it was quivering gently almost thirty feet away. He walked over to his knife and picked it up by the hilt. There was a gray rat impaled on the blade, its mouth opening and closing impotently as the life fled. He crushed its skull between finger and thumb. (Neil Gaiman, Neverwhere)