Childhood, Boyhood, Youth by Leo Tolstoy is a semi-autobiographical trilogy that examines the progression of a boy from childhood to his teenage years. As the title of each part suggests, the overarching theme is growing up and all of the experiences that come with the process. The first two parts are realistic in their depiction of a young boy's development, using natural language and realistic situations that make the character universally appealing.

The trilogy transcends time periods, race, and culture and is regarded by literary critics as relatable to any young male experiencing growing pains. The other theme of the trilogy is the tension, as well as balance, between naivety and cynicism. The boy is an idealist who wants to change the world, but he learns later on that the world and the humans that occupy it are more complex than he imagined.

Youth, on the other hand, explores the multidimensional aspects of love—whether it's romantic love, love for nature, or love for humanity—and how youth navigate through intense emotions. The story of the boy's development can be interpreted as a metaphor for the awakening of humanity, in which humans learn their place in the universe and embark on their quest to understand the nature of existence.