AMONG THE WORLD'S top architects, Rem Koolhaas may be the most influential. An energetic teacher—most often at Harvard's Graduate School of Design—and persuasive writer (his books include Delirious New York and S, M, L, XL), he has also mentored scores of young architects at his Rotterdam studio, the Office for Metropolitan Architecture (OMA), where pay is S and pressure XL. (American architect Joshua Prince-Ramus remembers that his first "day" on the job lasted 48 hours.) But Koolhaas's apprentices are rewarded with something more than money: Under his tutelage, designers learn to privilege approach over style....