Each book in Bastien Theory Boosters is a handy 6" x 9". The series coordinates perfectly with any method and introduces theory concepts with games, puzzles, mazes and riddles. Each activity book focuses on a single theory concept so it's easy for students to grasp one before moving on to the next. The twelve book series starts with Book 1 Naming White Keys and finishes with Book 12 Naming Accidentals. It's a fun way to reinforce theory concepts!