Actually "reading" in this instance refers to something you do when you're in a club with lots of vogueing (the gay subculture dance that Madonna ripped off). If you "read" someone you can instantly tell why their vogueing was lame or predictable.

Yeah, a lot of this comes from drag and ball culture- see Paris Is Burning. There's a lot of this stuff coming to mainstream attention lately, with the "Voguing" compilation on Soul Jazz, Mykki Blanco (who I've tried to submit but fucked up the URL), Azealia Banks (she even covers this track on one of her mixtapes), and Le1f (who is his own thing, really, but tends to get lumped together with the others in "queer rap" thinkpieces). It's fascinating stuff and there's some killer music there too.