This is a pretty good book, but my biggest problem with it starts on page 54, "The Structure of the Minor Scale". In it, Helen Cooper writes, "There are two forms of the minor scale...the harmonic minor and melodic minor." The problem is there are really three. She neglects to mention the natural (or pure) minor scale, which is really the most common of all three. If you play the first eight white keys on a piano, starting with A, that's the natural minor scale. She also doesn't mention modes at all, which the major scale and natural minor scales came from. The major scale is Ionian mode, and the natural minor scale is Aeolian mode.
The book I come back to over and over is "Every Musician's Handbook". Major scales, minor scales (all three of them), and modes are covered on pages 7 and 8.