I typically feel that 200 page books deserve more than a two sentence encapsulation, but in this case I need to make an exception. Virginia Postrel's The Substance of Style is best summarized as...
Design's everywhere these days, because everyone's a designer! Related finding: there's no accounting for taste.
And I had such high hopes. (There is one interesting chapter titled "The Boundaries of Design," which discusses, at length, the shifting role of city planners from zoning enforcers to taste enforcers, but I think it was interesting to me because of my long history with the people's republic...)