<p>I am not actually planning on taking the exam, I just want to teach myself above-beginner's level music theory as part of my process of teaching myself the piano. I'm planning on going through the theory portions of the three Alfred's Basic Adult All-In-One Course books and then teaching myself the contents of AP Music Theory. So I was wondering what prep book is best for AP Music Theory. I was considering Barron's but I heard that there are some downsides to Barron's. I don't mind textbooks either but a cheaper option is preferred. Thanks in advance for your inputs!</p>