The "Music Theory in a Nutshell Grades 1-5 & Theory Is Fun Grade 5 Book" is a beginner-level workbook written by Maureen Cox. This revised edition book includes 64 pages of essential music theory concepts. The "Theory Is Fun" series focuses on engaging students with fun exercises and activities to help them understand music theory at a beginner level. The book is suitable for those studying music theory with a focus on voice as the primary instrument.