This is by far the most entertaining book on music theory I have ever read. It is one of the most understandable and easy to read books on theory, too. The book covers all of the fundamental areas of theory from diatonic intervals to chord construction to tritone substitutions. Ear training is also covered as is the philosophy of improvisation (including tips for better improv.) I would wholeheartedly recommend that anyone new to music theory read the book cover to cover. Experienced musicians will find it useful as a reference.