In a closed urban fantasy, the magical world is secret and no one knows about it. In an open urban fantasy, everyone knows about it. So with a closed fantasy, you have to figure out how the world keeps itself secret, and with an open one, you have to figure out how knowledge of magic has altered the world we know.
Cassandra ClareStop it," he hissed in her ear. "You'll just make it worse for yourself. It's better if you don't look." "Like you do?" she hissed back. "Shutting your eyes and pretending something's not happening doesn't make it not true, Jace. You ought to know better-
Cassandra ClareThose girls on the other side of the car are staring at you." "Of course they are," he said. "I am stunningly attractive.
Cassandra ClareYou tried to drink the East River,"Magnus said, and Alec saw, as if for the first time, that Magnus's clothes were soaking wet too, sticking to his body like a dark second skin.
Cassandra Clare