The "Great Brain" is a fictional character created by author John D. Fitzgerald in a series of children's books. The stories are set in the early 1900s and follow the adventures of a young boy named Tom Fitzgerald and his brilliant older brother, The Great Brain, who is known for his clever schemes and ability to outsmart others. The series highlights themes of friendship, family, and the challenges of growing up. It captures the essence of childhood in a small town in Utah, showcasing the mischief and creativity of kids while also providing valuable life lessons through the experiences of the characters.