British journalist Rawsthorn capably depicts the neurasthenic personality of France"s famous fashion designer, born in Algeria in 1936. She really excels, however, in her savvy account of the industry"s transformation as emphasis shifted from haute couture handmade for the rich to ready-to-wear designed for the (fairly affluent) masses. Saint Laurent and his astute lover/business manager, Pierre Berg launched many trends, including the licensing of his name to adorn everything from sheets to sunglasses. A business book as much as a biography: nice work on both counts.