I checked this book out for E.L. Konigsburg's contribution, "Ruthie Britten and Because I Can," those being her answers to the question "Why do you write children's books?" Any of the authors' essays are worth a look, especially for people who are interested in any of the contributors. David Macaulay has a wickedly funny essay about creating children's nonfiction picture books, filled with dubious wisdom such as "Any clues in a picture, for instance, that might increase a child's awareness of and sensitivity toward his or her environment should be completely removed."
I didn't find the essay on nonsense verse illuminating at all. Ursula Nordstrom's essay on editing children's books is magnificent, although of course a lot of the specific business advice is centuries out of date now. The same goes for a lot of the pieces at the end about the children's book business, which are at best historical artifacts at this point.