Five-year-old Saroo, a poor boy separated from his older brother, rode a train alone for hundreds of miles. Not knowing where in India his hometown was, he was truly lost. After a harrowing ordeal on the street, he ended up in an orphanage. From there, an Australian couple adopted him and took him to their home in Tasmania.

Longing for home is, as the title implies, a primary theme of this memoir. Brierley's few memories, along with sleuthing and technology, finally enable him as an adult to locate his original home.

The idea of incompleteness of identity is likewise a strong theme. Saroo didn't lose the sense of belonging to his home country and family. The pull to find as much as he could, to regard himself as whole and authentic, powerfully shapes this poignant story.

The related, fundamental question, "What is family?" also threads through the narrative. His adoptive parents' loving upbringing together with their later support in his quest were crucial to his development. Saroo has to learn intellectually what a life of poverty had meant to his birth mother, who had few employment opportunities as a single mother. His appreciation for both aspects of his heritage offers another personal slant on the nature-nurture relationship that helps define kinship.