I discovered the the Wooden Books series less than a year ago through some serendipitous bookstore browsing, and soon purchased them all. Each volume is compact, well-written, beautifully illustrated, and most of all informative. I'm reading my copy of Harmonograph along with Stuart Isacoff's book Temperament (also recommended), and couldn't imagine a more perfect pairing of books. Being musically challenged, I rely on Harmonograph to make better sense of the intervals Isacoff discusses in his book, and it does so in a brilliant, unique way. You won't be disappointed in this little gem.