Alfred's Essentials of Music Theory: A Complete Self-Study Course for All Musicians
By Andrew Surmani, Karen Farnum Surmani, and Morty Manus
 
Recommended as self-study for advanced middle school or high school and up.
 
From the publisher:
 
This practical, easy-to-use, self-study course is perfect for pianists, guitarists, instrumentalists, vocalists, songwriters, arrangers and composers, and includes ear training CDs to help develop your musical ear. In this all-in-one theory course, you will learn the essentials of music through 75 concise lessons, practice your music reading and writing skills in the exercises, improve your listening skills with the enclosed ear training CDs, and test your knowledge with a review that completes each of the 18 units. Answers are included in the back of the book for all exercises, ear training and review.