If you love words, you will cherish this book. Ciardi is a knowledgeable, creative and funny man, which makes his explanations a joy to read. The preface alone is worth the price of the book. (And in that preface he mentions my favorite word origin story: where the word nasty comes from.)
Ciardi isn't a one-trick pony, either. Another of his books is "How Does a Poem Mean?" -- an introduction to poetic structure and meaning. And he wrote a book with Isaac Asimov called "Limericks: Too Gross". The man gets around.
You'll get a chance to read some of Ciardi's explanations of word and phrase origins right here tomorrow. (And you won't believe the great language of baseball post coming up this weekend!)