I took 4 yrs of theory and I still study it after school. Theory for me though is academic not practical. Theory itself is just the study of what has been done by certain people (Bach, Beethoven, Debussy) in the hope of understanding what works. The books I started off with as a beginner were Ottman's "Elem. and Advanced Harmony". I highly recommend these books cause they start with the very practical all the way up to modern and more advanced practices from guys like Stravinsky and Debussy. Simply put, these books are easy to comprehend. The bulk of the books cover harmony, but also hit important notes on melody, rhythm, form, and more. The books also contain exercises, drills, and techniques which I believe is very important because to fully grasp theory you must practice using it. Reading about it alone just won't give you the full understanding of it. These books show you how to do it and then asks you to do it with there examples and then with stuff that you write. On the negative side both these books will cost you about 150 bux. However they are a great start and you'll definitely see improvement in your muscial ability once you have completed them.

Paul Hindemith's books are also very good, however I think it is alittle harder to understand than Ottman's books. Also the bulk of his books use his own music as examples. However Hindemith is a good composer, it's better to learn from a variety of composers. Ottman goes through several of some well-known composers.

The book you ordered I have not looked at, so I couldn't give you an honest opinion.