`The Good, the Bad & the Difference' by Randy Cohen.(Knight Ridder Newspapers)

In the introduction to "The Good, the Bad & the Difference" (Doubleday, 277 pp., $23.95), Randy Cohen tells us how he, a former comedy writer for Rosie O'Donnell and David Letterman, became an authority on proper behavior. Cohen is "The Ethicist," whose New York Times Magazine column, in which he tries to resolve the ethical dilemmas that his readers find themselves in, is syndicated across the country. (It appears in this newspaper in the Saturday Religion & Family section.)

The book is not just a clip-and-paste of old columns. It has a lot of new material, including some "Ethical Pop Quizzes" _ hypothetical problems on which you can flex your own ethical ...