Pretty simple. He writes passages like this one (from The World Made Straight):
"Leonard turned and watched the red and white ride called the Octopus fling riders into the sky. Beneath its flailing arms, in the nexus of thick black cables, grease-caked gears, and pulleys, crouched a man in a grimy tee-shirt and jeans. He was old, brow and biceps wrinkled, long hair falling to his shoulders in a gray tangle. But he moved with the dexterity of a spider monkey as he hunched and scurried between the supports and electrical systems to keep the machine going, its wide arms appearing to hurtle forward but in reality returning again and again to where they had always been. Like God at the center of his universe, Leonard thought, watching the scabbed, grizzled hands at the controls."
A tiny world in a paragraph. I could almost live there for a little while.