A few of weeks ago I began compiling a (personal/Quondam) OMA/Koolhaas dossier (4813f-4813y), and, so far, I wouldn't say Koolhaas "design[s] his architecture through his writings or books." Certain design themes from "Exodus" and Delirious New York do recur throughout the oeuvre, however. More to the point, perhaps, it may well be that the now vast oeuvre itself continually breeds new design ideas.
On Bullshit by Harry Frankfurt. Not by Rem but it will help you understand him.