Book excerpt: Politically incorrect, comprehensively unscientific, and exceptionally funny, this guidebook identifies--and pokes fun at--the people of the Rainbow Nation. After sorting out the labels Black, English Whites, Afrikaners, and Coloreds, the discussion pushes on to more difficult questions: Why should you never give a White woman a white-gold engagement ring? Why do Indian men always play sports in jeans? and How do Colored gangsters fare in the navy?